I like the relay~mains idea best as well, turn everything off, pump/TEC/PC the lot!. any chance of a schematic/drawing on how to make a timer curcuit for 'the unwashed' like me?
. what chips, parts needed kindof thing. it's the thing every H2o rig should have, especialy if a TEC is used. make a good article. specialy if the sensor is as cheap as £13!, timer included would'nt top £20 probably!...