The Zubie Vehicle Tracking and Engine Diagnostic Device plugs into your car's ODB-II port and uses a built in T-mobile cell service (not your phone) to upload data that you can monitor via the free app.The Zubie App works with or without the Zubie key and can be a cross platform &#34;find my friends&#34;.  With the app you can view location of any family member using the app as well as set up groups of friends.In addition to getting the location of others in your group that use the app you can also track the location of vehicles that have installed this key in your family. If a family member is in a car with the key the app automatically associates them together.For each vehicle that has a key you associate a primary driver and this driver earns a driving score based on their speed, hard accel/brake, night driving etc. The app can also send instant alerts when these occur as well as instant alerts when a vehicle arrives or leaves a location saved in your &#34;places&#34; list. These places have a perimeter associated with them. So you could set a small perimeter to get an alert anytime they arrive or leave the location or you could set a large perimeter and only get alerts if they leave the general area as the perimeter can be anywhere from 0.1 miles to 25 miles. Each place has its own notification rules and can be set for arrival, departure, or both.Trip maps show the start, end, and actual path of each drive. Top speed, idle time, and locations of acceleration and braking events are identified. For the map view you can view individual segments identified by anytime the vehicle is turned off, or a combined view over multiple trips or even multiple days.The engine diagnostic codes are very helpful. I have seen temporary codes here that didn't trigger a check engine on the dash and anytime the check engine light is on you should find details here on the fuel, emission, or other system. The Zubie also has an indication for the vehicle battery condition.The Zubie service does require a $99.95/year fee which is the same price as a new key. So you could consider the key is free, or you could ask why you don't get a discount the second year if you already have a key...I highly recommend this product for teen drivers. I am not suggesting you watch their every move, but a driver that knows their status is being recorded should be more careful. And if you have an issue with the driver not being where they are supposed to be, then you can log on together and review the records. The $100 you spend here is well worth the results.The ability to get diagnostic codes remotely is a nice feature, perhaps not enough to justify a $100/year service on its own though.These are missing features that I hope the app adds in the future, these are NOT in the app as of this review.Ability to see speed anywhere on trip not just top speed.Gas mileage as well as driver feedback reports on a regular basis to offer suggestions on how to improve their driving and get better fuel economy.