TimeCounter Free (free.timecounter) on Google Play
TimeCounter is a universal time counter.It can record the cumulative time spent on a task or activity.The number of counters is unlimited (only 1 with the free version) and they can record simultaneously.The data displayed by the counters are customizable.An alarm of time spent can be scheduled for every counter.A hourly rate can be defined for each counter and the total value can be displayed.