When traveling to Singapore, I take my normal T-Mobile GSM phone with me and it “just works.” People can call my U.S. number and it rings and acts normal in Singapore. GSM phone service is in use in most places in the world, allowing you unprecedented uniformity of communications. Everything is great except that it costs $1.65/min in Singapore with a U.S. SIM (Subscriber Identity Module). Youch.

Naturally, I didn’t use the voice part of my phone very much when I’m here to avoid the terrible cost. Instead, I turned to Skype. Skype is a free internet telephony application and network that allows computer to computer calls for free using a broadband Internet connection. Skype’s strengths are its simplicity and it has been tuned for good audio quality under poor network conditions.

Computer to computer voice communications isn’t terribly useful most of the time, though. So in addition to that, you can subscribe to SkypeIn and SkypeOut. SkypeIn is where you attach a phone number or numbers in any number of cities to your Skype account. SkypeIn and SkypeOut are where Skype makes its money by renting you the numbers and charging per-minute rates.

When people call your SkypeIn phone number(s), your computer can receive the call just like someone calling you with Skype from another computer. SkypeOut lets you call regular phone numbers from your computer. These services, along with a bluetooth headset (earphone/mic combo) let my laptop communicate with any land or cell phone in the world for generally astonishingly reasonable cost (mostly where I call is 2 to 3 cents a minute.)

Now, one of the features of GSM phone service is that your identity (phone # and other stuff) is stored on a little smart card called a SIM. These cards can be removed from your phone and put into another GSM phone and that phone will then become the phone number associated with the SIM card. In the U.S., generally this isn’t done because cellular phones are sold “locked” to a particular provider. If you buy a phone from, say, Cingular, the phone will only work with Cingular SIM cards unless the phone gets unlocked.

In most other places in the world, this doesn’t appear to be standard practice. When here in Singapore, I tend to buy cell phones so my cell phones are unlocked and can work with any SIM card. In addition, when we are here, I buy a StarHub Green prepaid SIM service which gives me a local phone number that is very economical for voice and data locally (around 14 cents US/min)

The problem with that is that while the local SIM card is in my phone, my telephone # in the US will just go right to voicemail. While the US SIM card is in my phone, I get charged terrible roaming fees. What to do?

Well this time, I thought of a clever trick. Skype is testing a new service called Skype forwarding. This service lets you forward your skype account to another Skype account, or any phone # in the world — costing only as much as it would if you were using SkypeOut.

So, here is what I did. I installed my US SIM card in my phone. I turned on the call forwarding for my US number to forward to my SkypeIn number that is in the same area code as my US mobile phone. This allows me to receive calls to my mobile phone on my computer.

Next, I installed my local SIM card in my phone, turning it into a local prepaid phone. Using the Skype software (had to use a Windows version using virtual pc because the Mac OS X version of Skype doesn’t yet support the feature) I set my Skype id to forward to my Singapore mobile number.

The result? Calls to my US cell phone are forwarded to my Skype account, which is forwarded over the Internet to my local prepaid mobile phone.

The result? I can receive calls transparently from my US mobile phone on my Singapore mobile phone for around 15 cents a minute and the callers don’t really know any difference. Outgoing calls to the US, cost around 13 cents a minute because of #5 below.

There are a couple of gotchas.

1. SMS messages are not forwarded
2. Forwarding calls from a US mobile phone to another phone number still uses mobile phone minutes as if you were making a call from the mobile phone to the forward-to number. This is not a problem for me because my plan has sufficient minutes for all my calling and during the time that I am up here in Singapore, my cell plan is under the unlimited nights and weekends usually.
3. It isn’t real speedy to setup the call. It takes 5 rings on the caller’s side before my phone rings the first time here. Longer if Skype is online on my computer so I have a chance to intercept the call there before it goes to the local mobile #
4. There is a slight conversation delay because of the voice over internet thing, just like using Skype on the computer. Although the delay is less than the computer version, very tolerable.
5. Outgoing calls from the local phone use normal minutes for local calls and StarHub rates for international long distance. The reason I chose StarHub over the other providers here is that they are running a promotion that if you dial outgoing long distance with a special prefix (018) rather than +1 the long distance is “free” costing only local minute charges.

The world of VOIP (Voice Over IP) is changing everything. Telephone providers need to know that people will use the most straightforward service if the price is reasonable. If my roaming rate was even as high as 30 cents a minute, I would probably just use the phone normally. This scheme is not straightforward, but the price is fabulous. International roaming charges at $1.70 USD per minute is just stupid.