As someone who has been using Google Voice for nearly a decade, I completely understand its appeal. You are given a real, free phone number that you can provide instead of your real number. All calls and texts are forwarded to your real number. This is great for keeping your real number private and only giving out the Google Voice number.
Or if you’re like me and travel a lot, your Google Voice number can be used consistently to contact you, regardless of the local number you’re currently using.
Plus, Google Voice works as an independent cell phone number/service if you need it. As long as you have an Internet connection, you can make (and receive) calls and texts for free to and from any number in North America, no matter where you are in the world. You can also call and text non-US numbers at very reasonable rates.
Cloud
MySudo
MySudo is not open-source.
MySudo is a privacy protection service that offers a few different features to give you more control over your online identity. Masked emails, phone numbers and credit card information. This means that if your information is leaked, you can simply remove or change this “mask” to stop receiving spam (or block charges on your credit card) without your real information being compromised.
MySudo is not the only one offering these services. Privacy.com, IronVest were some of the first, but the concept took off and is now even included in many managers of passwords or even email services. What makes MySudo unique is that it also allows you to use this number to send messages and make calls (albeit with strict limits). The free teir does not offer phone numbers or cards.
Hushed
Hushed is not open-source.
Hushed is a dedicated VoIP service. While I can’t speak to their privacy, they do offer some very flexible payment options compared to their competitors. For the same price as MySudo, you get unlimited calls and texts from your new number. Although of course you won’t get those cool extras that MySudo offers. That’s why I decided to include both so you can decide for yourself which best suits your needs.
T-Mobile DIGITS
DIGITS is not open-source.
Obviously, you can’t expect any privacy from an ISP. I only listed this option due to the scarcity of alternatives in this category. But you should go with absolutely anything else if you can.
For T-Mobile subscribers, the DIGITS service is not only free, but possibly even better than JMP and even Google Voice. The main problem with the last two is that many services don’t accept “VoIP numbers,” which is what they provide. DIGITS doesn’t have this problem, as T-Mobile can actually issue real phone numbers. The only downside is that this service is only available to T-Mobile customers.
Self-hosted
JMP
JMP depends on the venerable XMPP protocol, which should work on your own XMPP server. If you want to ensure full compatibility with all JMP features, or for those who don’t want to self-host, you can choose to use one of the suggested XMPP servers.
You can transfer your number within one to two weeks and start making calls using the SIP client of your choice. SMS (text), MMS (image), emoji, unicode, shortcodes, delivery receipts and even group messages are all supported. You can try all of its features for 30 days to see if it’s right for you, as it may seem a little complicated at first until you get used to the quirks.
They charge a reasonable $34.99 per year, and it appears to have almost all of the features of GV. JMP is even available for devices that don’t have eSIM support via third party hacks. The beauty of open-source.
Vonage
Vonage is another self-hostable FOSS alternative to Google Voice. While JMP only supports North American numbers, Vonage supports a lot more countries! Beyond that, it operates very similarly to JMP using XMPP. Numbers cost anywhere from around a dollar all the way up to €1,500/month depending on the country.
As cool as all of this is, neither Vonage nor JMP are consumer-ready products. Rather, they are back-ends for developers to build polished solutions on top of. Like Cheogram.
Cheogram
Unike JMP and Vonage, Cheogram is not a service. Rather, it hooks into your (Android) phone’s backbone routes your calls through your JMP or Vonage server. It’s a fork of Conversations.im that they extended for this purpose. It even lets you continue using your phone’s default dialer!