Be aware that the OVMS module (at least the V3) appears to use more pins that most of the common engine monitoring dongles. Many extensions and Y cables don't work correctly -- there may be some telemetry, but some information and capabilites available with a direct connection won't work. The reason is that many cables only connect some of the pins.
It took me 3 tries (although I admittedly may have had better luck if I didn't go for the cheapest available... :) ) to get a cable that worked. The first one I didn't know there would be a problem, and the second one (despite being labeled a 16 conductor, straight through cable) was missing some connections. But persistence paid off, and I now have a functional module, where I want it, and with enough slack to be able to easily shift it around, if required.
If you're looking for an ODB2 extension, be careful what you select. :)
grnbrg.
What kind of cable did you end up using?
What vehicle is this for?
It really depends on the vehicle. OBDII really only covers the basic polling functionality to obtain engine and exhaust pollution emissions metrics. For electric vehicles that is not really relevant, and we often need to look elsewhere to find what we need.