Ebay is full of dual sim gsm or dual standby chinese phones which sell for decent prices and come with spare batteries, touch screens, memory slots and usb chargers. It will great if these phones are produced by reputed electronics company like samsung meaning better quality and customer service. There is a big market for these phones in europe thanks to expensive calls, and long contacts .Hope other operators like nokia and sony join as well with 3g offering , breaking the restrictive tariffs of companies like vodaphone and tmobile who try to lock phones and user experience of their customers by branding phones and removing all options and settings.

I think there was a "dual stand-by" Benefon. Perhaps 10 years back. You could receive calls on standby on any of the two SIMs at the same time, no switching. But you had to elect which one you want to place calls through and switch to place a call through the other one.

And speaking of switching in software, I still have an adapter for Nokia 3310, which allowed you to swich by pressing *3340# or something like that.

Two years back I did some marketing for a company called Amatus. ( www.amatus.biz) . We could have up to 6 different sims from different phone companies or regions of the world in a special carrier. The phone I personally had, ( a superb Sony-Ericsson 630) had 2 sim cards in it. One from Vodaphone in Spain, one from Amatus for travelling to Germany. I could have had up to 4. Though in my phone only 2 were active at a time. We needed the carier for up to 6. THAT was in the fall of 2006. Switching was automatic. Ironic, progress, no?

It has nothing to do about Signal or coverage. It is all about cost: usually each network offer very cheap calls to the same network, but makes it very expensive to call the other network… so many people are carrying two and sometimes 3 phones to make it easier for people from different network to call them.

But since you are not fro, a developing country, you make a strange assumption that it is due to bad coverage!!! Which is not true at all.