We've put one in our car. If you're worried about it chirping and alerting a thief with sound, then you can take part of the speaker out and it won't make a sound anymore. iFixit has a tear down, although they don't mention it for this purpose, you can figure out which part to take out. We've already done it, and all the chirping as gone. I guess the same could be done with hiding one on a bike too.
For $29 it's kind of a bit of fun, and not in place of a real tracker for cars, but it still works pretty good.
For $29 it's kind of a bit of fun, and not in place of a real tracker for cars, but it still works pretty good.