I was not aware that the URM-15T has a settable period of time after 
which it wakes up. I've put investigations into and support for this 
feature on the ToDo-list (=> not a promise, as I may not be able to 
get hold of a URM-15T here in Germany, but that makes sure I won't 
forget looking into it).

Regarding limiting the wakeup functionality to a certain remote: I 
don't think that'll be possible. The Keyspan receiver does not do any 
parsing/decoding of the raw IR signals it receives on its own. That's 
entirely done in the software on your computer.

Opposed to that, receivers like the one Apple builds into Macs limit 
wake up to specific remotes (here: the Apple Remote), but also do 
parsing/decoding of the raw IR signals in hardware. That's the 
positive aspect. The negative aspect here is that these receivers are 
limited in hardware to a limited set of remotes using the same 
protocol and thus lack the flexibility a "stupid" receiver like the 
Keyspan has.

Best regards, 
Felix Schwarz