Triad has this in their VST plugin. However, they just go up and down the list in order, including triplets, etc. Glitchy, for sure, but not that musical.
Even so, I use it a lot!
Now the reaktor delay I built just halves and doubles, and that's a lot more musical most of the time. It also has a control for the lag time (i.e. how fast you moved the head on the echoplex) which is really useful. I can set it really slow, and the echoes gradually start to lock up to the tempo, but the pitch shift just sounds like chorusing.... or I can set it slow and get abrupt shifts.
For a minute backin the 80s, I had a roland tr606, the matching tb unit, and an old effectron. I ran the bass cv into the effectron delay length input, and ran the drums through it. Very nice transients from the abrupt delay time changes, and nice polyrhythms depending on the pitches you programmed in the bass unit. Maybe you could get that on the FM3 with the sequencer modifying the tape delay's tape speed input? I'll have to try that tomorrow.