GyroDroid

So far Unity has only built-in support for a few sensors on Android mobiles.
This package provides access to every single sensor of your Android device, helps remove device and orientation inconsistencies, and just makes sensor-aware games work.

It can and has been used for augmented reality, multisensoric games, visualization and more.
GyroDroid also has experimental crosscompile support for iOS, including a virtual linear acceleration sensor.
Unity Remote 4 is supported.

See the forum thread for more information.

The package comes with several demo scenes (including a nice rotating robot). You can download the demo application from the Android market: goo.gl/gkFq7

(Type the link in your mobiles' browser to install the app. It is included with the package!)