News that Apple has patented a 'proximity detector' for use in a pen interface inevitably prompts speculation that it may be developing a Mac tablet to rival Microsoft's Origami ultra-mobiles.

The patent describes a smart surface that can sense the presence and position of a nearby object, allowing as a finger or stylus to control an electronic device without actually making contact with it.

There is nothing new in proximity control, which is possible on many existing tablet computers. Apple seems most likely to use its implementation on some kind of music player, seeing the Origami either as a dead end (as do a surprising number of industry insiders) or as a format that will take some time to establish.

Apple might be advised to hold back, learning from Microsoft's successes and mistakes, and waiting for the power-efficient processors and fast links like UWB that that will finally give us truly portable computing.

But a Mac ultra-mobile with the design flair of the Ipod would undoubtedly be a winner, even using today's technology, and it could kick-start adoption of the format.

If Apple waits too long, not only will it have to suffer the indignity of flogging 'portables' conceptually decades behind those of its major rival, but it risks being pre-empted in the market.

A basic Origami at the right price (sub-£400) could sweep the world, and consign all Apple's beautiful Ipods to history. And there are plenty of companies, like Samsung, with the money and market clout to do it.