We've supported accelerometers in GNOME/Linux for a number of years, following work on the WeTab. The accelerometer appeared as an input device, and sent kernel events when the orientation of the screen changed.
Recent devices, especially Windows 8 compatible devices, instead export a HID device, which, under Linux, is handled through the IIO subsystem. So the first version of iio-sensor-proxy took readings from the IIO sub-system and emulated the WeTab's accelerometer: a few too many levels of indirection.
The 1.0 version of the daemon implements a D-Bus interface, which means we can support more than accelerometers. The D-Bus API, this time, is modelled after the Android and iOS APIs.
Accelerometers will work in GNOME 3.18 as well as it used to, once a few bugs have been merged. If you need support for older versions of GNOME, you can try using version 0.1 of the proxy.
Orientation lock in action
As we've adding ambient light sensor support in the 1.0 release, time to put in practice best practice mentioned by Owen's post about battery usage. We already had code like that in gnome-power-manager nearly 10 years ago, but it really didn't work very well.
The major problem at the time was that ambient light sensor reading weren't in any particular unit (values had different meanings for different vendors) and the user felt that they were fighting against the computer for the control of the backlight.
Richard fixed that though, adapting work he did on the ColorHug ALS sensor, and the brightness is now completely in the user's control, and adapts to the user's tastes. This means that we can implement the simplest of UIs for its configuration.
Power saving in action
This will be available in the upcoming GNOME 3.17.2 development release.
For future versions, we'll want to export the raw accelerometer readings, so that applications, including games, can make use of them, which might bring up security issues. SDL, Firefox, WebKit could all do with being adapted, in the near future.
We're also looking at adding compass support (thanks Elad!), which Geoclue will then export to applications, so that location and heading data is collected through a single API.
Richard and Benjamin Tissoires, of fixing input devices fame, are currently working on making the ColorHug-ALS compatible with Windows 8, meaning it would work out of the box with iio-sensor-proxy.
We're currently using GitHub for bug and code tracking. Releases are mirrored on freedesktop.org, as GitHub is known to mangle filenames. API documentation is available on developer.gnome.org.
: gnome-settings-daemon, gnome-shell, and systemd will need patches