I have one of the trackers by
http://www.trackersecurity.co.uk/ fitted on my monster. It's not as fancy as the Bike Trac one, doesn't have a phone application but does the job and their service has been great so far (I never had to use them for anything else than false alarms).
Also it's a bit cheaper but requires an additional remote control to work properly with a bike since this is designed primarily to do geo-fencing so unless you get the remote there's no easy way to turn it on/off.
On the downside, it is a bit bulky and might prove difficult to conceal it in a motorbike depending on the model and how much free space you have
