This seems cool and all, but wouldn't it likely violate ToS of your carrier by doing something like this -- especially if it gets to be of any appreciable scale?
Obviously it depends on what you do with it and the terms of your provider and local regulation. Spamming is forbidden if done manually too, you know? So is probably abusing "unlimited" plans with high throughput if you read the fine-print of your contract.
For a personal SMS gateway so you can have mobile network access without having your personal location tracked, it should be fine.
