In our ward we share a google doc spreadsheet among the Bishopric members. One of the clerks updates it after each Sacrament meeting, with it sorted in date order. to record the speakers and prayers. The Bishopric members can easily sort it by name to see when a given member last spoke or prayed in Sacrament meeting. It doesn't exactly tell you who hasn't spoken, but with it sorted by name and compared to a ward directory, you would easily see what names aren't there at all.