A heartbeat is a so-called event that is issued by the Flexwhere for Desktop (formerly TrayApp). Flexwhere knows which user is logged in at which location.
Flexwhere for Desktop records different events so flexwhere can show where a person is. A heartbeat is delivered every minute. For example, Flexwhere for Desktop shows the user's status in Flexwhere.
Read also: Is Flexwhere for Desktop necessary to use Flexwhere?
Read also: What events does Flexwhere for Desktop give?