HipChat (hipchat.com) is a personal messaging service that lets users create rooms to have one on one or group conversations. The service has been around since 2010, but there is no native Windows Phone app, just some decent third-party ones.
That may change, though, assuming you let the HipChat team know your thoughts on the matter.
The group behind HipChat solicited a request for feedback for Windows Phone users on Twitter and Facebook about making a native app. From their Facebook page:
"We have heard that some people on Windows Phone would love to have a native client to run on their phone. Chime in and let us know what you think if you are one of those users."
This request sounds straightforward to us. So head on over there and let them know your thoughts (follow our source link)!
Source: HipChat Facebook; Thanks, Joel S., for the tip!