I actually just finished building an MVP of a product business with a friend that we're launching later today: https://www.burnerphone.us
Essentially, we sell these pre-paid disposable cell phone kits that 'expire' after 30 days of usage (and come with unlimited talk and text, nationwide US coverage).
We actually built the thing with security in mind, specifically because of the incredible amount of information that's now gathered not only by phone companies, but by the government as well. Want to make a phone call that won't be personally associated with you, from telephone company phone records? If so -- you really need to use a separate device (a Burner Phone).
Anyhow, sorry for the plug in this thread, but thought it could lead to an interesting converstation.