This is an Gentoo overlay offering a series of packages useful for tablets and convertible laptops, where one would wish to have things like auto-rotating screens, on-screen-keyboard and do something with low-level sensor data like gyroscopes and light sensor.
The repo is not available through layman at the time. In order to use it you have to clone it locally and then edit your make.conf file.
PORTDIR_OVERLAY="<PATH_TO_YOUR_REPO>/tablet-repo/"
There are several packages. This overlay provides IIO-Sensor-Proxy to access sensor and expose them through DBus. This packages is dependant on SystemD.
You can install it with
emerge -v iio-sensor-proxy