I don't know any way to do it now. Would certainly require 3d party software, and I don't know if the developer's kit supports use of the audio chips that way. I doubt it. (Voice recording is directly linked to a dedicated chip, I think.)
I've just gone through the shopping/eval on digital recorders. I really like the RipFlash products. Unlike any others I've seen, they record direct to standard formats -- MP3 or WMA.
Unfortunately, only the WMA version (
http://www.pogoproducts.com/ripflash_dx.html) uses an SD card. I decided on MP3 (for one thing, getting the recording onto SD in WMA doesn't help me play it directly on the 7135) -- and that comes only in a SmartMedia version. I bought this one:
http://www.pogoproducts.com/ripflash_plus.html.
I'm having no trouble using a multi card reader to transfer the SmartMedia recordings to a desktop computer, then immediately to SD card. So I can play the recordings without modification on the 7135 and get them there pretty easily.
My next step will be to try the Enounce plug in to slow down and speed up MP3 desktop playback, to assist with transcription.
By the way, the RipFlash product is very small and can record for many hours. The built in microphone is more or less adequate for voice; results are much better using a preamp mic.
Any line-in recording is fabulous -- I've used it with the Radio Shack (43-1237) phone recording adapter and also used it to directly record and convert to MP3 any sound I can play on my desktop computer. For instance, I had access to a recording in the DSS format used by other digital recorders, software for which is awful. I played it through the speakers, but threaded the speaker cable first through the RipFlash, and recorded while playing. Presto, perfect fidelity in MP3, any bit rate I wanted.