For folk that are worried about the costs of GroveStream, I've been at it about 10 months or so and I think I've paid a little over three dollars (total) for the service. That doesn't mean it can't cost more, the more you do, both input and output, raises the cost, but a little care and you can easily keep the costs down.
I'm not collecting transactions and throttling the upload, I send all measurements every minute. So, if I ever want to, I can easily collect for a few minutes and send them up as a group. So, when the expense gets to the dollar a month range, I'll look into that. For now, 10 months, less than 4 bucks, isn't worth worrying about.