I have an Avermedia AverDigi NV5000 card in a pc, with remote viewing. Currently it is monitoring 4 cameras. It uses my sprint pcs card that I use for my rural internet connection.
I love it! It sends me emails to my phone/work wherever if it sees certain objects or motion. I can even view it remotely on my pda phone (windows media, or symbian based phones). Remote viewing on the web is pretty smooth, and the view on my phone is pretty much realtime, with some minor lag. Makes me feel somewhat better i guess...
I would think that any of the big three, Sprint, ATT or Verizons mobile broadband services would hit you in some way. Check the websites out and see what the coverage area is. If you do any surfing, you wont regret it!