Hello, hope you are doing fine. 

You can have it installed in many devices, but if you want top use it in many devices, that really depends on the type of device that you are using. 

If you are using a cable modem or if you are using a gateway (modem and router combined) such as the models: SBG8300, G34, G36; because of the modem part that allows just a single coaxial cable connection, the app would work in one device only. 

If you are using a Wi Fi mAX router, such as the models W21, W31, etc;  you can actually have the app installed and use it in more than one device. 

Hope this could be helpful!