What are some alternatives?
When comparing Vitelity and Eir SIP Voice, you can also consider the following products
Google Voice - Google Voice gives you one number for all your phones, voicemail organized in an email format, free...
Phonebooth - Phonebooth is one of the leading voip providers, providing phone systems & phone service for small businesses.
BVoIP - BVoIP allows to easily add Cloud & On-Premise VoIP PBX to the product offering without having to re-invent the wheel or add another layer to the daily operations..
VoIP.ms - VoIP.ms is a VoIP origination and termination tool.
Mitel - Business Communications and Collaboration
Loop Communications - Loop Communications provides hosted VoIP business phone systems to small businesses and mid-sized companies.