How do I get the Grasshopper VoIP app to open automatically when a call comes in?

How do I get the Grasshopper VoIP app to open automatically when a call comes in. Calls always go to my telephone service if I don't have the app open (which keeps the caller on hold a lot longer). And I don't want to have to remember to open and keep open the GH app every time I reboot. GH provided no assistance other than to say some phones do, some don't. And if they adjust my phone, it may effect other apps.

The only way would be to set the default app for Phone to the Grasshopper app, and then all your calls would come to it. As they said, some phones work well with the app, some work not so well.