Skype launched  an iPhone application today which lets you make and receive Skype calls over WiFi (but not cellular). We have often compared femtocells with UMA, which can also be used to send cellular mobile phone calls over WiFi. Both femtocells and UMA must be provided and managed by your mobile phone network provider. Skype and others provide a third way, installing a VoIP (Voice over IP) application in your phone which bypasses the mobile phone network completely and uses WiFi and the internet to connect your call. Will Skype undermine the business case for femtocells?

Skype is very popular

More international minutes are now carried over the Skype network than any other individual operator - some 33 Billion of them annually according to analyst TeleGeography, of which over 8 Billion are chargeable. This doesn't make Skype the wealthiest of businesses because its rates are extremely low (it's parent eBay is trying to sell it). I've found Skype particularly useful when calling home from business trips - by calling to a home PC, I can also share video - and when making international calls.

Skype is very easy to install and use, overcoming many corporate firewalls and other obstacles. It's feature range includes dedicated SkypeIn phone numbers in many countries, so you can pretend to have offices worldwide. Conference calls and voicemail are also available. Although it uses proprietary protocols and codecs, it is now able to interconnect with standards based VoIP services using SIP.

But it's primary use is for voice

Yes, it's true that Skype can also make video calls, but the main value and usage is low cost voice calls from point to point.

It also includes a file transfer feature, which can be helpful to send through the presentation or document you are talking about.

But this isn't the same as a full web conferencing system like Webex or GoToMeeting. And Skype isn't used for web browsing, instant messaging, email or other data oriented web applications. (But I do find Skype's plugin for Firefox useful - it identifies any phone numbers on webpages you are viewing so you can make a call with one click).

And it's not Anyplace, Anywhere, Anytime

We are becoming used to being able to make or receive voice calls and send/read email messages anywhere we go. Our mobile phones work at home, in the office, and when out and about.

In order to benefit from Skype you really need to be sat down at your computer with an already paid for internet broadband connection. iPhone, netbooks and laptops allow us to use Skype from Wi-Fi hotspots when you are out and about - assuming they are available. The compact size of the iPhone makes this more convenient, but still somewhat inconvenient.

But fundamentally, you can't count on being connected by WiFi when you're not at home or in the office. If you know you're going to make a long or international call which would be expensive, you can often make arrangements to sit down somewhere to take the call. There are other low cost ways to call internationally or connect to conference calls using your phone instead.

Other more complex products try to make this more compelling

There are a couple of alternatives which have closer integration with the phone system:

• Truphone , which currently works with Nokia smartphones, provides you with a new mobile phone number.

• When on WiFi, calls are routed in a similar way to Skype, and at similar low rates. 
• When out and about, they use the traditional mobile phone network. 
• When making an international call, the system dials a local number then routes the rest of the call via WiFi.

• Fring , which works on Windows Mobile devices, supports a wide range of internet services including Skype, VoIP providers, Instant Messaging and Twitter. It automatically logs into your favourite Wi-Fi hotspots on your behalf  to save hassle of reconfiguration each time.

These certainly do work, but are seen to require more technical knowledge than the average man-in-the-street is prepared to invest.

Anywhere, anytime, always on is still worth a premium

The saving grace for mobile network operators today is that the straightforward anytime/anywhere/always on capability of cellphones is hard to match, and certainly worth paying a premium for.

Where alternative  systems work seamlessly and either save significant money or provide good indoor coverage, then they are worth looking at. Examples of expensive international or lengthy calls might make the case.

So Skype isn't a direct competitor for femtocells yet

• Skype is for voice calls, not web browsing or other data intensive services
• Skype won't offload lots of data from the cellular networks
• You can't easily use your cellphone number for Skype
• It needs a WiFi capable phone, rather than just any 3G model

Skype Website: