Twilio, or Vonage, maybe? A lot of the phone stuff as a service thingies are more b2b focused, and a lot less easy to use and integrate than Google Voice (if you're not using them as a company).
Also saw some people reccomend voip.ms, but I have no personal experience with them.
JMP is the bees knees, couldn't be happier with the service. The app takes a little bit of getting used to, but once dialed in it can function right along side your phones main number. Zero issues with it working on websites too, highly recommended!