You can reboot most S60 3rd Edition devices by calling Starter.exe from Python, but this doesn't work in 3rdEd FP2 phones (tested in N82 and 5320 XpressMusic).
Example: e32.start_exe(u'Starter.exe', '', 0)
Anyway such a reboot functionality (officially supported) would be very useful in Series60 devices, because of memory leaks, hanging network and bluetooth connections etc. In many cases software restart and automatic start at reboot resolves those problems.
(I'm developing an application which must stay mostly functional continuously several weeks without user interaction.)