The N810 is mechanically USB OTG compliant!! No hacked/modified cables or the like are required for host mode!

I just verified with an off-the-shelf Micro-USB-A to standard USB-A cable (part no AK 676-AA from www.reichelt.de).

The Micro-A plug (which is mechanically and electrically different from the Micro-B plug on the cable nokia supplies with the n810) fits perfectly into the recepticle of the n810 and switches it automatically into host mode. Thus the n810 accepts both, the micro-a and micro-b plugs which is exactly what it should be able to do as an otg device and which the old n800 unfortunately can't due to its Mini-B-only recepticle.

This is cool news as this means that all usb compliant adaptors should work. Unfortunately the cable from reichelt i bought is slightly "weird" as it has a standard (male) A plug at the other end. This doesn't make much sense, a female A recepticle or a standard B connector would make much more sense, but reichelt only sells those weird ones. Other places have Micro-A to standard B cables. This is typically what you want.