Design and build a wireless timer for students giving talks.  The student tlaking would have an LCD display that counts down the time left in the talk.  A green LED could come on at some time as a warning, followed by a red one (and a buzzer?) closer to the end.

The person moderating the talk would have access to the timer through a web page.

The project is not incredibly difficult, but there is a wide variety of  tasks (hardware/software/networks…) and the system must be robust and low power.