Just a quick follow-up to this - if you have one and don't mind damaging it, the Nokia CA-157 cable can be made compatible to USB hostmode on the N900 by simply grinding the connector down to fit. It so happens I just bought another AC-10X charger off eBay, and it came with a bunch of N8 cables thrown in, including the CA-157.

The idea is not new, you can find any number of references to users making it fit a Samsung Galaxy S2 here on Google, so I figured hey, if it works for them it must be electrically compatible, and promptly took a drill-mounted grindstone to it until it resembled a USB micro-B connector. I managed to rip up part of the top of the plug, so I ground that off as well.



It's still a fairly tight fit, about like a new charger, and I wouldn't do this without a well and truly reinforced USB port. You have been warned. But, it works perfectly fine; I've just connected it to my primary phone, plugged in a standard Nokia USB cable and a second N900, and mounted the eMMC of the second phone without incident via hostmode-gui, so it seems to be a fully working USB OTG cable, the only problem being that as supplied it doesn't physically fit into the port on the N900.

Obviously, USB OTG cables are a matter of a few pounds on eBay; most users should probably just buy one. But, if you happen to have a CA-157 that you don't mind grinding down, it works fine.