I fully understand what you are suggesting and the idea is good, although I doubt it will make much difference, as getting any amount of money will be enough to make people steal them anyway, just look on any bike forum people steal $60 Xmart bikes all the time.Yet again I have to repeat myself GeeBee. It's about theft prevention not on road detection. As I've posted so many times, having to have a registration document and number plates prevents worthwhile sale, so prevents theft in that way. The number plate does not need to be huge or prominent, just fitted, since it's not about detection of mobile offences like speeding etc as it is with motor vehicles.
The key thing is the owner's registration document, without which the bike, just like a car or moped, is practically unsaleable.
Plus once the registration idea comes in I suspect what I talked about will be the unfortunate end result, I am fairly certain it would be in Oz.
A good lock and an alarm system might be about the best defence, not ideal but better than nothing.