By JR Rodrigues, Technical Advisor — REFINE Technology

The electronic monitoring industry is seeing a quiet but significant shift toward wrist-worn tracking devices. Sold as “more discreet,” “less stigmatizing,” and “consumer-friendly,” these wristband-style GPS and BLE monitoring devices are marketed to agencies looking for lighter-touch supervision options. There is genuine appeal in a device that looks like a fitness tracker rather than an ankle bracelet.

But there is a fundamental engineering problem with nearly every wrist-worn electronic monitoring device on the market today: inadequate waterproof protection. And the consequences of this inadequacy go beyond device failure — they create monitoring gaps, false alerts, and legal vulnerability that can undermine an entire supervision program.

In my career spanning Qualcomm RF testing, hardware design at 3M Electronic Monitoring, and VP Engineering at a European EM vendor, I have disassembled dozens of monitoring devices from multiple manufacturers. The wrist-worn category consistently shows the weakest environmental protection — and the reasons are rooted in physics, not manufacturing negligence.

Why are wrist-worn monitoring devices more vulnerable to water damage?

Wrist-worn devices face a fundamentally harder waterproofing challenge than ankle-mounted devices, for three reasons that have nothing to do with manufacturing quality:

1. Higher water exposure frequency

An ankle monitor contacts water primarily during showering, bathing, and swimming. A wrist-worn device contacts water during all of those activities plus hand washing (10-15 times daily), dishwashing, cooking, cleaning, and any activity where hands contact water. The cumulative water exposure for a wrist device is 3-5× higher than an ankle device on any given day.

2. Thinner form factor constrains seal design

Consumer expectations for wrist-worn devices demand a thin, sleek profile — typically 10-15mm thickness. An ankle monitor at 20-25mm has substantially more internal volume for seal grooves, O-rings, gasket compression space, and secondary waterproof barriers. Wrist devices sacrifice waterproof engineering margin for aesthetic thinness.

Consider the math: a seal groove that provides 2mm of gasket compression at 24mm device thickness would need to be proportionally thinner at 12mm — but thinner gaskets have less compression tolerance, meaning they are more sensitive to manufacturing variation and thermal cycling deformation.

3. More flex, more stress on seals

The wrist is a high-mobility joint. Every hand movement — writing, typing, gripping, twisting — flexes the strap-to-case junction. Ankle joints flex during walking but experience less rotation and lateral movement. The constant micro-flexing at the wrist progressively fatigues waterproof seals, particularly where the strap interfaces with the device housing.

What does the IP rating landscape look like across wrist-worn EM devices?

When you survey the wrist-worn electronic monitoring devices currently marketed to corrections and pretrial agencies, the IP protection picture is troubling:

The pattern is clear: the wrist-worn category, as a class, delivers significantly lower waterproof reliability than professional ankle-mounted devices. This is not because wrist device manufacturers are incompetent — it is because the form factor itself makes IP68-grade waterproofing exponentially harder to achieve and maintain.

How does water damage manifest in monitoring programs?

Water ingress in an electronic monitoring device does not always cause immediate, obvious failure. More often, it creates a cascade of degrading performance that erodes program reliability over weeks:

1. Intermittent GPS drift: Moisture on the GPS antenna reduces signal sensitivity, causing position fixes to degrade from 3-5 meter accuracy to 50-100 meters — triggering false zone violation alerts
2. Cellular connectivity drops: Water on the cellular antenna or SIM card contacts causes intermittent signal loss, which the monitoring center sees as “device offline” alerts
3. Tamper detection false positives: Moisture on proximity sensors or strap integrity circuits creates electrical noise that looks like tampering to the monitoring platform
4. Battery swelling: If water reaches the lithium battery, chemical reactions can cause swelling, reducing charge capacity and — in extreme cases — creating a thermal safety risk on the wearer’s body
5. Complete device failure: Eventually, accumulated moisture shorts critical circuits, and the device stops functioning entirely

Each of these failure stages generates operational cost: officer time investigating false alerts, device replacement logistics, supervision gaps during device swaps, and — most damaging — erosion of the monitoring system’s credibility in court proceedings.

What should agencies consider when evaluating wrist-worn devices?

Wrist-worn devices have legitimate applications in low-risk supervision scenarios — alcohol monitoring compliance checks, curfew verification for low-risk pretrial defendants, or as companion devices paired with a primary ankle monitor. But agencies should apply rigorous due diligence:

1. Require IP68 minimum with thermal cycling data — reject any wrist device rated below IP68, and require documentation of thermal shock testing (not just static immersion)
2. Request field deployment data specifically for wrist-worn use — a vendor’s ankle monitor deployment data does not validate their wristband product
3. Plan for higher replacement rates — even with IP68, wrist-worn devices will experience higher failure rates than ankle monitors due to the inherent form factor challenges. Budget accordingly
4. Verify the manufacturer’s criminal justice track record — has this company served corrections agencies, or is this a consumer wearable company entering the EM market? Manufacturers that have never deployed in any criminal justice environment — including their own domestic market — represent elevated procurement risk
5. Consider ankle-mounted alternatives for high-risk populations — for any supervised individual where monitoring continuity is critical (DV cases, sex offender monitoring, flight-risk pretrial defendants), ankle-mounted devices with proven IP68+ protection remain the reliable choice

The CO-EYE product line illustrates the difference in approach: the CO-EYE ONE ankle monitor carries full CE-certified IP68 protection validated across 200,000+ deployments, while the CO-EYE i-Bracelet wristband (a 17-gram BLE companion device with 2-year battery) is specifically designed as a paired device for in-facility identification and low-risk monitoring — not as a standalone GPS tracker exposed to daily shower-to-cold cycling. The engineering team made an explicit decision not to position a wrist-worn device as a standalone outdoor GPS monitor because the form factor’s waterproofing limitations cannot be fully overcome at any price point.

Frequently Asked Questions

Are wrist-worn GPS monitors as reliable as ankle monitors?

No. Wrist-worn devices face 3-5 times more water exposure, tighter form factor constraints on seal design, and higher mechanical stress from wrist flexion. Nearly all wrist-worn electronic monitoring devices have lower IP protection ratings than professional ankle monitors, leading to significantly higher field failure rates.

What IP rating should a wrist-worn monitoring device have?

IP68 is the absolute minimum for any device worn continuously in criminal justice supervision. However, even IP68-rated wrist devices will experience higher failure rates than IP68-rated ankle monitors due to the form factor’s inherent waterproofing challenges. Agencies should plan for higher replacement budgets.

Can a wrist-worn device replace an ankle monitor?

For high-risk populations requiring continuous GPS tracking, ankle monitors remain the reliable choice due to superior waterproof protection. Wrist-worn devices are appropriate as companion devices for in-facility tracking, low-risk curfew monitoring, or alcohol compliance checks where continuous outdoor GPS is not required.