Pardon me for this comment but that thought of leaving something in your bike wouldn't work here, I mean it is not applicable in this part of the world. If the thief couldn't detach the gadget from your bike, for sure he would take the bike instead. Even motorcycles which have its own lock are sometimes taken. Some thieves here use a pickup for that purpose of stealing bikes and motorbikes.
On a brighter note, some big malls are now providing a parking for bikes and motorcycles although they are still no guarded which gives the thieves a little chance to do their thing.