Yep, it can be done. I used the opto trick to work a button on an audio processor. Long time delays are sometimes difficult to achieve. You can take two of these kits: **broken link removed** that could provide a basis for the design.
You would also need a power supply kit that can supply 12 VDC, the opto, another led and a resistor. You'll need a plastic case because you want RF to pass through it, standoffs and a bunch of other little stuff. You can get the kits assembled if you really want to.
We could make a power supply for the remote too so it doesn;t require batteries. You could mount the remote permanently on the top of the case so that it's accessible, but not removable.
So, I would envision a LED to show power and another LED to show the timing pulse. You would mount everything into the box. The case and the power supply cost money too.
It's not the cheapest solution, but it's one that isn't that hard to do either.