This has taken me quite a while so I hope at least some people find it useful 
I’ve seen a few Imp powered bootloader based programmers for AVR MCUs.
But I wanted a full featured in-system programmer so I came up with this…
All the code is available on GitHub and I’ve put together a way over long blog write-up of the whole thing here:
Please don’t be put off by the length of the post - the actual setup and usage is really very simple.
I’ve attached a way impressive animated GIF showing an ATtiny85 that has just been programmed by an Imp to flash an LED
Programmers have come up a couple of times on the forums before with people like @aron, @generjones and @hugo.
Would be interested to hear what you and others think - hope’s it’s fun/useful.
Regards,
/George