check out M&S for a nice mobile site - they auto detect the operating system and serve an appropriate site - not looked at what they do re dupe - I think the mobile site is blocked but because they detect if you search via a phone you end up in the right place.  Apparantly during busy periods instore they get people ordering on their mobiles rather than queuing.

You might want to look at Mippin.

Wo good examples. Think m&s have won though.

I will check them out more. Thanks.