I have just installed Air Mouse on the ATV and my iPhone.
It’s quite a cool pointing device FWIW.
Unfortunately I cannot get the keyboard on it to work. So for example, I can navigate around a FireFox screen and click on links etc., but I cannot type in a new URL in the URL box, a search term in the search box, or credentials into a web page etc.
On the AirMouse virtual keyboard on the screen of my iPhone, the letters I type are indeed registered, but nothing appears in FireFox.
I am on fresh install of ATV OS 3.0.1.