The answer is just about everywhere! WatchTVeverywhere works anywhere you can receive an Internet signal: inside your house, at the office, shopping mall, hotel, airport, vacation home, etc. Wired connections and in-home WiFi will provide the best quality.
The quality of watchTVeverywhere signals while roaming (airports, stores, etc.) will vary depending on the strength of the signal. Be extra careful when you travel, especially outside the U.S. Data roaming charges may apply to networks that allow access outside the U.S. and they can be very expensive.