Well, you'd want to make it a /bit/ more generic, surely? Like, "load this url and send a text to this number if the (page text | diff) matches this regexp"?
Even allow people to create presets that would then be added as a generic thing. You could use it for camping all sorts of intermittent online things (web site specials, online ticket pre-orders, etc.)
There are many sites which already does this. During that situation when I missed a slot, I didn't want to take any chances again by using sites like visualping. I trusted my script and twilio API to work.
First I thought to ring a loud alarm connected with a Pi, but then it will be limited to my apartment. So I went with twilio to give me a phone call. Because I should act immediately and time was of the essence. Emails or SMS might go unnoticed.
Even allow people to create presets that would then be added as a generic thing. You could use it for camping all sorts of intermittent online things (web site specials, online ticket pre-orders, etc.)