Alarm Systems

just get a decal for your front and back door--if youre on a low floor, put a few on some windows, too

Try Franklin Report:'Telephone Systems' http://www.franklinreport.com/SearchProviders.aspx?m=NYC&s=40

Do it yourself. Its not hard. I bought the wireless equipment from:
http://www.homesecuritystore.com/
then signed up and hooked to http://www.geoarm.com/ for the monitoring service which is alot cheaper.
a) you own all the codes and equipement
b) no bogus ridiculous mark-up on the monitoring service.
c) you can choose where to put the hidden 'contacts' (ie internal drawers or switches for silent alarm)

At the end of the day if someone wants your stuff they can smash and grab...or just tie you up..
The stickers mean the most 1 on the main door, 1 on the fire-escape window.

How common is this? Anyone do this in a doorman building?

Yeah I agree. I bought a diy alarm system from the guys at link pro communications:

http://www.go-linkpro.com/DIY-Home-Security-System (looks like they are re doing their website right now)

And also got monitoring setup through alarm relay for $8.95 a month.

Step number one is the yard sign and window stickers to keep burglars away. So I would start there and when you can afford it get a system and monitoring.