Summary: Get 2 phones. A smartphone(or tablet) and a basic phone. You keep the smartphone offline and use it for offline maps & WiFi. The basic phone you use with either a local simcard or a global sim like sims2go and a callback provider like VoIPDuniya.
^ this is gold, and since I've never seen anyone come up with it, prehaps you read it here first!
I'm currently sniping on ~80 auctions to win a Nokia N80.
This should help someone with my lifestyle in multiple ways:
1) GPS for navigation
2) Cheap VoIP calls over WiFi
3) 3G is now ~£5 a month for 2gb
I'm using JBidwatcher and sniping at £50. It seems my discussion of the phone may have brought prices up in the last week, from average £55 to about £70 so it may take a long time.
For anyone interested in such a phone the battery is a pain, you need to work at saving battery time. Personally I'll keep a camera phone as spare.
If you need advice for Internet or phone calls on the move get in touch.
Could this be useful?
All solutions have drawbacks. Why can't we just go anywhere and be have free incoming calls??
1) Local simcard (need to be there a while)
2) Find internet/WiFi (Fring or VoIPCheap online call initiator)
3) International simcard that doesn't charge incoming calls for the country you're going to
4) SMSBug txt and ask them to call you back to a phone box or hotel reception
5) Commit to Voda passport or similar (need to travel the whole month as it's only on a month by month basis)
6) Some countries (i.e. Madagascar) have stalls with mobile phone where you can hire someone's phone to make or receive a call
7) 3G internet local to the country
8) Satellite internet and VoIP
The best solution I have found is to use:
simstogo.co.uk in the mobile, they have good rates but the main thing is that they have managed to secure free incoming calls in quite a few countries but very regretably, not all by a long shot.
It works something along the lines of you attempt a call, which is not allowed, this is sensed by them somehow, and they call you back. I don't know quite how they've done it but it's very clever.
You can combine this with initiate calls with SMS or internet (voipcheap phone-to-phone), however, with the SMS solution you will have to configure the message centre number everytime you use a new network(and country). Network switching can happen quite a lot. Also, some networks don't work with simstogo.co.uk so if you have a problem you have to select the network manually.
As a result simstogo is great thing to have but it's still far better to get a local simcard if you can and go with that. Just make sure you get the person selling it to you to show WAP/internet and SMS txt messaging working first.
Hope this helps!
3rd update:: 17/1/2011
The best I have found is to use SimsToGo in combination with a callback service. This can be initiated by a website, by calling a set number (which doesn't complete and calls you back), or by sending an SMS. The best of all those of course is the Callback option.
Thus, the best out there is SimsToGo in combination with a callback service.
4th update:: 23/12/2011
In terms of choosing a phone it might be a good idea to have 2 phones. One you use for smartphone stuff and one for... a phone! Just keep the smartphone offline to save battery and credit.
And the normal phone you might want to go with something ultra small. You might use one phone for a local simcard and the other for your home network just in case; if charged to recieve calls you reject it and call them back on the local simcard with a callback service like VoIPDuniya.
You might use a watchphone, or perhaps just a really small phone. Both can be cheap, but are they useable enough?
...I'm currently using a Nokia E71 & SE W850 (got a rooted NookTouch N2E but haven't used it as much as I'd hope)... I'd prefer a Cellphone watch and mirasol display android tablet.
The speed of GPS fix is really important too. I find the E71 is way too slow. Sometimes it won't even fix. I find by the time you got a fix you've found another way to do it! The only one I know that is a lot better is the iPhone4S. I'd like to know how this is on Android tablets. The advantage of the $50 tablets is if it gets stolen it's less of a pain... but is the GPS actually usable?