Zebras ZAMS solution is designed to solve the same problem, but comes after it from a different angle. With the ZAMS solution it doesn't use they gyro or try to detect whether the device is in motion or idle for periods of time. Instead the ZAMS solution is all based on users logging into the devices to check them out. The accountability of the device associated with an individual end user is what drives the better process behavior around having devices placed back in the charger while they're not in use. The system can be configured to only let the user check one device out at a time so if they leave for the day without returning their device they won't be able to check one out the next shift so you're able to track down lost devices within 24 hours of them being misplaced. You also can configure alarms to go off if the device has been away from the charger longer than a configured shift so that people can find lost or missing devices out on the floor. It has an alarming system that achieves the same goal that you probably have, but it does so via a check in/checkout process with end user accountability versus your method of using gyro data. It is a licensed solution however. I'm not aware of anything available for free nor do I think anyone would develop such a solution for free as there is a fair amount of ongoing maintenance to support a solution like that, not to mention reliance on cloud infrastructure in a lot of cases.