You can install the Genie S-TV on as many devices as you like, but can only play the number of lines that you subscribe to simultaneously. As an example; if you have a household with 5 TV's and rarely watch more than 2 at a time than a 2 user account will suite you just fine. 3 user accounts can watch 3 TV's at the same time, and 4 user accounts can watch 4 at a time. Genie S-TV can be installed on as many devices as you like, so add it to your cell phone, game console, android device & firestick. You can always upgrade to more users, so buy the package that fits your needs.