iPhone as wifi hotspot?

Often I'd like to use my laptop when I'm travelling. If my iPhone can connect to the Internet, why should I buy another device & subscription for that laptop... I'd like to use that iPhone as my own hotspot.

Is this possible? Eg the iPhone connects over UMTS/HSDPA/GPRS to the Internet, and functions as a bridge. Eg creates a local wifi hotspot. Or allows the laptop via bluetooth to connect to the internet...

Any ideas? is this out there already?

Best regards,
Simon