Do not show “away” automatically. Allow the user to either set the idle time length or over-ride it and set their status to available. Every job does not entail someone typing on a computer all day. A person can be available and next to the machine but not actively using it. Some have to use multiple machines for security purposes. Just because you are not using a particular machine does not mean you are either “away” or “unavailable.” Many workers don’t have single task jobs. The application needs to be applicable to more than “cube farm” environments.
Additionally, there’s a phone app. Of what use is the phone app for mobile use if a person is set to “Away” or “unavailable” automatically... when they are available BECAUSE of the phone app. Availability while “Away” is the singular purpose of the phone app. Basing a persons availability or access to them off one metric is impossible.
Let the user override the automation when it is applicable.