If you work for a telco you may think high roaming charges are a good thing, but most of us find the bill-shock one of the most galling mobile experiences going.

As a result, there are many roaming charge avoidance strategies: from leaving the phone at home, to buying a special SIM, to trying to use WiFi-only at the venue or hotel. Here’s another, just in time for Mobile World Congress in Barcelona.

Simgo is one step up from buying a SIM to use when travelling. The big problem with that ‘buy a new SIM’ approach is that you lose the use of your usual number for incoming calls.

A company called SimTEQ is offering Simgo, a complete ‘virtual roaming experience’ for a per day price (up to so much data and minutes).

Before departing the home network the user diverts to a unique geographical number in the home territory. The calls are then forwarded to the travelled-to network or networks on a dynamic basis. Outgoing calls just go out over the host network in the usual way.

For all this to happen, though, the user has to remove the usual SIM and insert a new one attached to a rubber sleeve which houses one extra chip with configuration data on it (see picture above).

It’s hopefully easier to do than write down.

There are a couple of snags. So far there are only sleeves for the Samsung Galaxy S3 and iPhone 4 and iPhone 4s (more models to come this quarter), and the phones presumably need to be unlocked, since they’re getting a strange SIM shoved into them.

However, for unlocked iPhone and Galaxy S3 users (there are quite a lot of them) this ‘could’ be the roaming answer.