Gary has developed a touch event fuzzer for B2G that can be run on devices. It's called orangfuzz - https://github.com/mozilla/orangfuzz.
It uses orangutan (https://github.com/wlach/orangutan) to generate random touch events on a B2G device.
It's primary use case currently is to catch crashes. In order to run this in production, we'll probably need to wrap a test runner around it, and add some result processing capabilities.
> It's primary use case currently is to catch crashes.
We should also be able to catch Gecko assertions as well, with a debug build.
Bug 857843 tracks catching Gaia errors in B2G.