So I've actually been doing this in various forms for the past few years. Mind you I actually chose to go with Plivo (a competitor) instead of Twilio, a decision I'm still thinking about to this day (MMS primarily). The way it works for me is I actually use Slack as the interface to my contacts. Each person is their own private slack room. I use it just like any other, I send them slack messages and it sends them a SMS and vice-versa. So far it's been pretty great, I get to take advantage of all of Slack's clients and I just write the code that transits the messages using the Slack API. What's really fun is that I'm starting to allow slash commands so that my friends can use some of them in the rooms with me and we can have sort of a shared chat-bot experience over regular SMS.

If anybody is interested in seeing the code, some parts of it are already open source[1]. The most interesting piece is the dialer, as someone in the thread pointed out, setting the caller ID on the outbound is tricky. On Android there are actually APIs that can intercept outbound calls, manipulate the number, and make the call to my gateway and then input the actual number as DTMF codes followed by a terminator. It doesn't always work but in 95% of cases I've never had a problem.

[1]: https://github.com/saarons/ward

This is a clever way to handle the client. I like it.

I'm doing this.

I initiated a port of my primary number a few weeks ago.

I'm not sure if what I'm building is exactly parallel to Google Voice but I believe it's similar. I'm in Canada so I can't get Google Voice. I rarely use my phone's voice or sms functionality so right now I'm just forwarding transcribed voicemails (with mp3 link) to email, and sms's to email as well (replying to an sms with an email that goes to sms is sort of fun). I'm also in the process of building out a simple app to handle this.

While testing, I've noticed the best part is now I'm not tempted to answer a call that most likely doesn't matter. I simply get a notification with an email. And I won't be paying for my voice or text plan which was about half the cost of my previous plan.

If anyone wants to use this you can email me at shawnp at gmail dot com.

Me. I'm about to travel around the world and I'd like my friends and family to still be able to contact me at my current number while I'm away. I'll be getting prepaid SIMs and presumably a new number wherever I go. Twilio should allow me to forward just calls from a whitelist (telemarketers/scammers be damned) and only at certain times, since my timezone will be changing frequently.

Used to work at Twilio and definitely had this thought a lot. It's harder than it seems, at least to make it reliable.

Inbound forwarding is easy. Setting caller ID on outbound is where it gets hard in terms of user experience.