Unfortunately, others have already beat you to it.
For example, https://cheapglobalsms.com/
I went a slightly different route --- an old spare phone with Ultra Mobile PayGo prepaid SIM. For $3 per month you get 100 minutes of voice, 100 texts and 100 MB data per month.
The reason for this is that some security providers throw a little kink in the works by actually making a call to verify your number on sign-up.
