I use IFTTT to send myself multiple text messages a day, to which I respond and log the results in a Google Doc spreadsheet. Each month I blast past the 100 message limit. I've asked IFTTT to let me pay them for more messages but they said no.
Use Twilio, and have a stub of code inject your responses into your Google Docs spreadsheet. 1 penny per text message they receive for you, $1/month for the number.
