Yellix is a startup focussed on integrating Facebook with your phone's telephony, i.e. when someone calls you, their Facebook avatar and status are automatically popped up on screen, giving you an idea of where they might be or what they're up to. There's a native S60 3rd Edition version for download, the service is free and you can start using it immediately. Bandwidth used is reportedly low, only 3k for each avatar/status pop-up. See below for a hi-res promo video, a bit from the press release and see also their FAQ page.

From the press release:

“With the free mobile application YELLIX we take the phone call experience to a new level by adding relevant web 2.0 content to calls in real time”, explains Claudia Poepperl, founder and CEO of adaffix, the company behind YELLIX, about the benefit of the service. “YELLIX is the next generation caller ID system that includes the profile picture and Facebook status. That way YELLIX offers the world’s largest and fastest-growing community an immediate bonus”, continues Poepperl.

“YELLIX for Facebook was especially designed for viral marketing within the community. Everyone can invite their Facebook friends to YELLIX or download the service directly from the Facebook application store (http://apps.facebook.com/yellixfb)“, states Poepperl about the marketing approach. Users can also check which of their friends are the most loyal; each personal YELLIX-account on Facebook includes a list of the most frequent callers in the category “Your Calls”.

The free application was built for smartphones and runs on BlackBerry, HTC, LG, Nokia, Motorola, Palm, Samsung and SonyEricsson phones that support one of the following mobile Operating Systems: Android, RIM BlackBerry, Symbian S60 or Windows Mobile.