I would recommend T-Mobile. I'm using a Blackberry Curve 8520 using their unlimited data plan, 500minute unlimited text plan. $70.71/month to month/pay as you go plan.

The EDGE service is spotty, like Boost but they also have sufficient selection of 3G and Android phones.

I am in a unique situation. I am using a GSM phone with GPS mainly as a location sensor. So, I don't need any voice minutes, just unlimited data, for as low a cost as possible.

3G would be nice, but don't even really need 3G.

Other than spotty coverage, Boost fits the bill perfectly. They have unlimited data for 0.35c per day.

Most of the information in the Boost Mobile section is completely wrong. They run on Motorola's iDEN network primarily although some of their recent phones run on Sprint CDMA. Those CDMA phones do support 3G as part of their Power Vision network. CDMA does not use SIM cards, iDEN does but they are by no means GSM.

So, no. You can't use an iPhone with it.

Did you miss the part where the page also says Android?

I am using a Motorola i1 running android with a sim card in it.

If you are traveling to the US, one of the cheapest ways of getting a data plan without a contract is to buy a prepaid Motorola i335 for $30 - $50 with a prepaid connection and tether it for 35c / day.

The point of the site is to find out where to purchase a prepaid GSM SIM to use in an existing phone. Not where to buy all new equipment on an unreliable service.

Are you sure that Boost mobile works for iPhone? Their coverage seems to be limited to iDEN and CDMA, neither of which is compatible with iPhone's GSM requirement.

I am using Boost on the Motorola i1 which runs Android. I haven't tried it with the iPhone.