The hand-held concerned is the Zoom H2 but I see no reason why it shouldn't work for any other make or model.
Having installed Reaper onto an SD card then loaded that into the H2, and connected the H2 to a laptop via a USB cable, I was able to access the Reaper folder on the SD card in the H2 and run the Reaper exe, then in Reaper to open a file elsewhere on the same card, edit it, render the result back to the H2, and having disconnected it from the USB lead, play the result on the H2.
The Reaper installation used only about 8Mb on the 2Gb card.
Because the H2 only has "full speed" USB2 the speed wasn't as fast as if operating entirely within the PC, but it was usable. In fact I got 16 256kbps files in the H2 to play on 16 Reaper tracks simultaneously. Wave files would have maxed out the connection much more quickly I'm sure.
The point of doing this would be if you wanted to be able to plug your hand-held into any PC that happened to be to around, if away from base, and edit your audio without needing to install anything at all onto the "host" PC.
Reaper can be installed to USB storage devices by means of a batch file provided in the Reaper program directory.
I suspect the same could be done with the Wavosaur stereo editor too, which though more limited in function would take up even less space.
Portable apps rule! You could equally well have your Thunderbird email and your Firefox browser in your H2 (etc) too.