Haven't tried the Yi, but I have successfully used a Gitup Git2 Pro for wireless RTMP streaming. It supports connecting to wifi in client mode out of the box (i.e. it connects to a network, instead of hosting the network). You can add a VLC Video source in OBS and point it right at the camera's IP.
It works, but the resolution isn't great and the latency is quite bad. It was delayed by 3+ seconds (!!!) because the default network-caching setting in VLC is quite high.
The development version of OBS adds a Network Caching setting in the VLC source properties, just not in the released version yet. I built this from source and can toss the plugin file to anyone if they need it.
This lets me set the network caching down to ~500ms. Any lower and the stream will cut in and out. Not great, but acceptable enough for a DMD cam.
You could also futz around with delaying all your other video sources to sync up, but I don't bother.
I use it for a wireless camera rig that's easily movable when I don't have enough setups for every game. I use a HDR-CX405 with a Monoprice wireless HDMI transmitter/receiver for playfield, and the Gitup camera for DMD, all connected to a USB battery pack.
I'd also be interested to hear people's experiences with other action cams, too -- Especially if it's possible to RTMP stream with one of the super-cheapy ones over wifi in client mode (maybe with custom firmware?)