We have used this system to provide internet phone service for the past several years. The only ongoing cost was $5/month for taxes, billed through Ooma.com.
From the website:
Ooma is a full router capable of prioritizing voice data and directing traffic to ensure the most reliable phone service.
A USB port supports Wi-Fi and Bluetooth accessories and provides future expansion opportunities.
Built in speaker provides the ability to screen calls prior to answering.
A keypad provides one-touch access to voicemail.
DECT radio supports up to 4 wireless handsets. Ooma.com Retails for over $100