Lots of posts on theft already. The only thing new I have seen is GPS trackers with text messaging. I am not sure what you do when it starts ringing your cellphone. I would also start with a less desirable bike, take your seat post with you. Or go with a small wheeled folding bike.
2000 Montague CX, I do not recommend it, but still ride it.
Strida 3, I recommend it for rides < 10mi wo steep hills.
2006 Rowbike 720 Sport, I recommend it as an exercise bike.
1996 Birdy, Recommend.
Wieleder CARiBIKE (folding), decent frame.