You can fit it to the frame in a couple of ways, quite easily - all you need for that comes with the alarm.
You don't get a key but you get to set a secret code (if you forget the code you are in trouble

you will have to put up with the alarm till the battery runs out)
I'm very impressed with it and it's so funny to look at people's faces when they come to park their bikes and hit your bike accidentally
You can set the level of sensitivity, I had mine set so that it'd need to be moved for 3 seconds before the alarm goes off. The actual alarm is very loud so don't try inside the house.