$4.00 Bike Alarm with decent reviews

I got one of those, they work great-well for a bit I thing the vibrations from the motor screwed it up a lil, it takes much more to set it off now, used to be very touchy

I guess I know what gadget will be going on my bike next.

I've had one for a couple years, works well enough. It's sensitivity is variable tho. Sometimes it's touchy and other times it takes a lot to make it go off.

One time I forgot I set it and it didn't go off until I had already started my bike and shifted to 2nd gear!

I have one of those as well. I used it a few times when it was new at places my bike lock wasn't a 100% guarantee. For instance a place close enough to where I would be going in wouldn't have a good pole to use my bike lock but may have a kinda tall concrete parking pole that is maybe 5 foot tall. It was very sensitive when I used it. Its on my DS-20 now but I hardly ever use my bike to go to the store since I have a jeep now and the store is really close. Its nice to have just in case and its nice and tucked out of the way. For 4 bucks you cant go wrong. You never know when it could be handy. We spend so much time and moolah on our bikes this little gadget is a nice add on to a good chain and lock. Both can be beaten or broke but together they add another barrier for the bad guys to get through. Which could be just in time to save your ride. Most thieves can easily beat a lock and chain but if this thing is going off they don't like that attention and would probably make most give up right away.