I can voice chat with Happy coder. Also, I run happy coder in a sandbox of mine on my computer. What do you mean by syncing? Happy coder syncs sessions between all my happy coder clients. I can even see in real time how happy coder in my browser's conversations progress as well as on my phone, in parallel.

Happy is an abandonedware unfortunately. It's a great app and dev can capitalize a lot from it but for some reason he hasn't been seen or heard in months since the last release.

There are attempts to create a fork maintained by other developers, but they're yet to be launched.