Large external touchscreen support would be a killer feature.

I see it as being a 7" screen with a docking slot in the side (just like an oversized memory card slot) where you slide the phone in which then makes a connection with a micro HDMI connector.

Of course, the stumbling block would be power consumption and that you'd still be lugging a great 7" screen around with you.

I have got a couple of 7" mini DVD satellite screens. Trying to figure out why I don't get a display via the N900's AV out port and if there's a workaround.