Smartphones have a staggering amount of data they can monitor, and not just in terms of the Internet. Position, orientation, speed, sound, light, g-force, the list goes on - that's why academics are using them as self-contained sensor stations for cool stuff like blasting into space. If you need to monitor data remotely for decidedly less cool reasons (like seeing if your CDL contractor got four tons of gravel to the worksite without stopping at Arby's first) Valarm might be the right service for you.
Valarm monitors a handful of variables on a remote Android device: Accelerometer, GPS, light sensor, and other variables like battery life. It reports its data back to Valarm's servers, which you can access through its website. While it's hard to think what an individual consumer might use this for beyond a little gas expenditure tracking, it could be invaluable to employers or research institutions. The data can be graphed to maps, exported into Excel or Google Earth, or plugged into a public API.
Data triggers can be set to do everything from taking a photo to sending a text, and it's possible to upload only from WiFi hotspots - useful if your devices are tablets or non-active phones. The app can also harvest data from compatible external sensors over USB or Bluetooth. It's a pricy app at 5.98, but that buys you access to the more basic set of tools on Valarm's website. Advanced tools, data exporting, and fleet tracking require require credits - 15 cents per device per day, or a little less than five bucks a month for each device.