I'd just be a little concerned about other technologies making their IP and systems obsolete or irrelevant...
You can now get wireless Skype and Messenger phones for the home, and you can get clients for both for Windows Mobile and other platforms.
Large scale WiMax implementations could assist, but you will not get the coverage - especially if large telcos start to see the technology as a threat.
It certainly has a niche - just that I see it as a niche and not a high growth area.
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