This is one of those things I have been trying to look up for years but can't find the right query. Thank you!
It is a really weird device.
The Mylo was interesting because it looked like a cell phone, but it did not have the ability to connect to cellular networks. The idea was: Everyone is using AIM, Google Talk (or whatever Hangouts was called at the time), Yahoo messenger, VoIP, and so on -- why connect to cellular at all when those applications are all free over wi-fi?
So it came bundled with a handful of messenger apps and a "streaming" mode where you could send music files to your friends P2P. I think also some version of Opera browser?
At the time it came out, I tried to tell me parents it would pay for itself, since they were still on a pay-per-text plan. Look mom, texting will be free and you won't need to keep me on the phone plan. They didn't understand what I was talking about.
If the iPhone hadn't come out the following year, could the Mylo have killed mobile? Probably not, but I'd like to think so.