With these phone add-ons, who needs a PC?

With this in mind, it could be doing a lot more for you than it already does. In fact, the theory goes, why have another computer at all when you could just pop your phone into a dock and use it for almost everything.

There are already phones out there that will let you do exactly that. But due to marketing rather than technical constraints, they are still a long way from the consumer mainstream.

The first attempts at a modular phone, two or three years ago, took the PC approach of using ungradable internal components you could snap in and out to suit your purpose or as new versions became available.

Google and LG were among the big players backing that idea, but development has been largely discontinued and it has fallen to Motorola to take up the mantle. The latest version of its £380 Z2 Play handset is accompanied by optional accessories which clip on to the main body and include gaming controls, an extra-long battery, an optical zoom lens for the inbuilt camera and a mini-projector for sharing your business presentations or slideshows.

The phone is a slimmed-down version of the more powerful Z2 Force, which is expected to sell for close to £600 when it eventually launches in the UK. But the phones are of similar physical size and can take the same range of accessories. In fact, most are backwards-compatible with some of last year’s handsets.

The more interesting modules are a £70 pair of JBL speakers which clip to the back of the phone, turning it into a small but resonant boom-box, and that ten-fold zoom lens by the revered Swedish manufacturer, Hasselblad.

There isn’t another phone on the market with a 10x optical zoom lens, so this really does put the Motorola in a different class. However, its overall performance doesn’t compare with a quality standalone camera, and at £200 for the lens, plus the price of the phone, the Moto arrangement starts to make less sense.

The projector attachment, at £250, is better value, assuming you can justify the need for one at all. It’s capable of throwing an image nearly six feet wide, though not at high definition, and there’s no fiddling about with cables before you get a picture. On the other hand, miniature cube projectors which will slip into your briefcase if not your pocket, can be had for a similar amount and boast a longer throw.

Motorola’s wireless charging module is an addition more universally useful, and at £40 just about qualifies as an impulse buy. A few more like that and you could see the system really starting to take off - like a high-tech version of the craze for snap-on covers of a decade ago.

The Z2 itself is a handsome model, with a metal body, a 5.5in screen, an eight-core processor and a battery that is claimed to take seven hours of charge in just 15 minutes. It also has three or four gigabytes of memory - which is comparable to many PCs but without the overhead of having to run Windows. That means that even without the accessories, you could quite easily hook it up to a keyboard and monitor and run Google’s full-screen word processing and spreadsheet apps.

You might not need even the Z2 handset; try it with your existing phone this weekend.