[mindslight]

It's been a while since I looked, but the cheapest US paygo plans are still at least $3/mo (eg H2O wireless), and probably double that if you want more convenient billing. Have you found something better, or are you deriving that much utility from scaling to many devices or what? I'd think if the goal is signing up a bunch of accounts, one would be content with a single plan or maybe two, and just periodically swapping their phone numbers.

It seems like it would be easy enough to change your setup to hide your actual location by locating the gateway elsewhere and backhauling with its own IP connection.

BTW are there any standard interoperable formats for transmitting/presenting/archiving text messages, akin to Maildir for email or SIP for voice? If not, maybe Maildir is the right answer.