I'd buy an iPhone if it came with a trans-dimensional portal to any parallel universe I wanted to explore. That would redeem it's otherwise Apple-flavoured crapiness.

An iJack would be useful too - a hardware add-on that converted audio from an input jack to an output jack. It wouldn't be any real use, but I suppose someone somewhere would realise you could put guitar effects inside an iPhone and turn it into a very fragile guitar stomp box.

Just having a bloody 3G modem you could use with a bloody Macbook Pro would be a major achievement though.