The following unit seems to fulfill all the needed requirements that I have seen for muscular work:
http://healiohealth.com/tek9.asp?pg=products&specific=johmnrcrq
The downside I see with it, however, is that it only has two channels, so it seems like it would be hard to do both hamstrings at the same time with the cross-over pattern from the CFTS book. How effective would EMS be if you could only apply two electrodes to each muscle, rather than the crossing pattern? 10-15 minute per muscle group is already a long time…