Moog should start making them…
Until then, check out Arturia’s Moog Modular V (V stands for Virtual). I have created a preset available for download based on the Ondes Martenot.
http://www.arturia.com/en/mmpresets.lasso
Click on my last name - Naegellen - and you’ll hear an mp3 sample.
the ondes martenot sounds amazing. i remember on a particular SNL episode where Radiohead was the musical guest they used one of them!
Forgive me if this has come up already, but somebody beat them to it. Analogue Systems’ French Connection (I think that’s what Radiohead use, most of Jonny Greenwood’s modular is made by them). Of course if Moog made it, I’m sure that it would sound better 
Steve
Yep the one Jonny uses is the French Connection. He uses an RS8000 modular synth (i think it has a sequencer too) also made by Analogue Systems. High priced stuff tho! That vsynth based on the martenot is not too bad.
yeah, that controller is ridiculously priced…but still awesome…
it would be a fun diy project
The ondes Martenot is far more than just the Analogu systems French connection. that will give you about 10% of the original instrument. As for emulating this instrument digitally, just forget it!