I've been meaning to experiment with the Arduino I've had around for years. A couple of hours of dinking around and downloading libs and I've got a functional programmable keyer that I can set into "low power mode" (uA?) . Nice! The keying string is almost infinite in length if needed and given that it's programmable, it can be buried in loops in loops in loops giveing a variety of messages, etc. Cool!
Oh, the best part? Buying from banggood.com or similar outfits, the mini versions of the arduino are less than three dollars DELIVERED in the US. Yes, I'll have to hang a single transistor on the output to key a transmitter but that's not any sort of problem.