Mark Bridge writes:

Watch almost any American TV show from the 1960s - I’d recommend a good police procedural - and at some point after a few episodes there’ll be a scene in a restaurant. One of the main characters will be dining and their meal will be interrupted by a waiter bringing a telephone to the table. The phone will probably have an implausibly long cable, although there may be a telephone socket nearby.

As the detective left the office that afternoon he’d have said something like “call me at home on 555-0743 if you need me. Then I’m off to the Channel 37 studios - you can reach me there on 555-0242 - and finally to the Electric Banana club. That’s 555-0322.”

Yes, mobile phones have definitely made life easier. And yet there’s something missing. Something really obvious that manufacturers have celebrated - and networks don’t want to talk about.

You see, the do-everything mobile device doesn’t. The Swiss Army smartphone is a fiction. One phone + one number = one straitjacket.

Going to work?  You probably want a smartphone. Going mountain biking?  Hmmm. Rugged smartphone, perhaps. Or just a rugged phone. Maybe something that’s smaller than a smartphone. Out for the evening?  Pocket sized, definitely. Well, tiny bag sized, at least. Taking photographs?  Wouldn’t it be great to have a SIM card in your DSLR. You could send high-quality images straight from your camera - and with a Bluetooth headset you could make calls as well. Using a tablet?  Using a laptop?  You hardly need a phone at all.

Yes, mobile phones can handle more than one task and more than one environment - but at some point we end up compromising. In fact, I don’t think there’s any other multi-functional device we compromise on so much.

Cars, to an extent, are another compromise. But that’s pretty much it. We have clothes to suit the weather and our mood. We have shoes to handle the rain, shoes to make us taller, shoes to help us run. We’ll put a different sized television in different rooms. But mobile phones?  We’ll get by with just one, thank you.

Yet the last 25 years have seen mobile phone designs for almost every situation. The Nokia 7280; as fashion-crazed as Lady Gaga’s high heels. The LG Chocolate. The Siemens Xelibri range. Bang & Olufsen’s Serene. Motorola StarTAC. Sony CMR-333. Ericsson R380.

Some of these were reasonable all-rounders. Others were ‘special occasion’ phones.

This week’s announcement from Sony Ericsson includes a handset I’d add to the list. The Sony Ericsson Mix Walkman is very much a music-oriented device, with a ‘Zappin’ key to preview the chorus of the next track and a karaoke function that lowers the volume of the vocal track to let you sing along. Very clever. However, there are also times I want a 4-inch screen. Or an 8-megapixel camera. Or a QWERTY keyboard.

There was a period when I didn’t have to choose. Around ten years ago I could subscribe to MultiSIM from Vodafone UK. Up to 10 SIMs, each in a different device - but just one telephone number. You could make calls from any of them and could ‘activate’ one to receive calls. There were some similar services from other networks but the Vodafone option is the one I remember. However, it had one little problem - and that quickly became one big problem. It couldn’t handle GPRS or 3G data. As BlackBerry ownership grew, soon MultiSIM was no more.

Curiously, there’s been no replacement. Maybe that’s because we’re more prepared to accept compromises. Maybe the rectangular smartphone design is becoming something of a standard. Maybe mobile networks have won - and manufacturers have resigned themselves to building compromised smartphones.

Or maybe, just maybe, networks have seen the future. Maybe they know that telephone numbers soon won’t matter to us. Our phones will identify the people we’re calling from their email addresses, their Facebook pages or their Twitter IDs. My contact list will be in the Cloud. The person I’m calling is connected somewhere, via something - perhaps an internet TV, perhaps their car.

When that happens, it won’t matter what phone we’re calling from or which phone we’re calling to. And that means we’ll be able to buy as many fashion phones, smartphones and tablets as we want.

After all, why should mobile networks care about putting ten SIMs on a single subscription... when they can sell you ten subscriptions instead?