I didn't think about that ... that may be the case. But it's just mirroring the display, so ... it's not really 1080p resolution - it just upscales what's on your phone to 1080p. I don't think it's actually rendering 1080p. it's possible that it actually rendering gfx for two different screens - but really I dobut it. I think it just upscales, and the upscaling is done poorly.
Aboyut the OTG cable - I have one for my motorola bionic. It's very cool, but the bionic's OTC cabability is ... severely cripled in how you activate it. The bionic requires incoming power on the otg cable, AND the outgoing power (which is required to power the usb device) is almost non-existant. So - to make it work you need to use a usb hub (hub provides power to device(s)), and you need a Y cable with both ends plugged into the hub. 1st end of y cable does the data connection, 2nd end of cable provides power - reson you need 2 ends: most usb hubs don't provide power on the same port the 'host' device is plugged into, but if you modify the hub to force it to send power then you only need one cable and not a y-cable.
Anyway, most device that support otg don't need a contorted setup like that. I read about a guy that modded the usb hub he was working with so it would supply power, and he would only need one cable and not a y-cable, then he went even further and he connected a phone battery to the usb hub to supply power (via a converter so that it supplied prober voltage, and he threw in a on/off switch). That guy knows his electronics!
That site I showed you sells those clips for the ps3 controller, and also the otg cable you'll need. cable is a bit more expensive than you can get it from amazon, but it's still pretty cheap.