Better visibility if someone is on a call
Add an option to show when someone is on a call, being in a meeting or busy, clearly, than just the red dot. This was a feature in Skype, where the status was clearly visible along with the name and the color of the dot.
This helps people to know what status the other person is really on before a chat ping or making a call.
Erik Cordua-von Specht commented
Additionally it would be helpful to have a button available that will not just hang up on the incoming caller but give the caller the message (IM) that the person is on another call. There does not appear to be 'busy' style ring tone...
If when you make a call the availability status showed as font in centre screen then you can choose whether to continue to make the call.
It helps in the scenario you haven't checked the status before dialling.