Ok well I found this dirt cheap circuit board which seems to do what I want. According to the engrish PDF:
[Function 10]:
Trigger Mode:contain delay off function, the relay does not operate after power
on ,give CH1 interface a high pulse signal, the relay pull-in immediately, when
the high pulse signal disappeared, the relay still pull-in, when arrived the setting
time T1 relay disconnect, the T1 can be adjustable between 0 second-270 hours.
Remark: in this function, if T1 is 0 second, give CH1 connector a high pulse signal,
http://www.ebay.com.au/itm/121324088350?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
And at $8.09 its the right price :P