Source: snapvoip.blogspot.com

We have seen enough models and accompanying advertisements for VOIP Phones, Hybrid Phones, dual mode phones, Video phones, wi-fi phones etc.
So I set out to search VOIP Pay phones. Not many products out there yet. I did find a few far eastern companies producing them.
But I did find an Australian company that has product in deployment. pieNETWORKS has created VOIP PayPhone as Hotspot Webphone, which allows one to:

* Provide cheap phone calls through VOIP
* Provide broadband internet access
* Provide Hotspot wireless access
* Provide Digital Media to advertisers
* Remotely manage your network of devices
* Extract detailed statistics and reports of usage
So they must be finding a market in travelers and unconnected users. Although cell phones have reduced the use of pay phones everywhere, one can still find someone putting coins into one of those. So it might be a niche that might work. But very rarely I see people at airport kiosks that provides similar services here in USA. I have never used those.
May be they out to place one of these phones next to those kiosks.

Links;
pieNetworks
Tongya VOIP payphone