Just backed. Very slick.
Been researching pay-as-you-go data SIM cards as well. Found a T-Mobile reseller Lyca Mobile for $0.06/MB with free SIM card http://www.lycamobile.us/en/national-plans
Others have recommended Truphone: http://uk.truphone.com/personal
I expect data to be only used when bike is stolen, so pretty much a free security precaution (albeit with spotty T-Mobile service). That is, unless I'm missing something.
I recommend Telna mobile
Free sim, but $19 per year charge.
Personally, I've been using a GeoGram One since it is based on Arduino and very configurable, but requires DIY. I like this Shy Spy for the guy who wants an easier setup (albeit with less options)
That gets you 1000 outgoing text per month and unlimited incoming. There's no way you'll exceed that with a spy kit unless you steal your own bike everyday.
Especially since these devices send/receive SMS rather than data, it's like having service for only $19 per year!! Runs on TMO's GSM network as well
Get a Cycle Analyst and a Multimeter, you're still a noob if you don't have at least one of each.
Planning on posting questions or buying anything on this site? Put up your country (at minimum) on your profile. This is a worldwide forum and we haven't reached clairvoyance.