It seems possible.

Maybe the device could also measure skin conductivity like a lie detector machine, if REM had some correlation with moister levels on the skin, I am not sure if it does or not.

I had a idea of implanting a suit with hundreds of small vibration motors, which moved in sync in such a way that made the person feel like he was moving. My thought is that something like this could help induce WILDs.

This idea just came to me, what if instead of light or music a cloth arm band had a small vibrating device which went off when the machine detected REM state. If you could do this without waking the person up I think it would be a good way to go about it.