There's tracking apps available for your phone. For example Oudie Live will Bluetooth GPS position to your phone which then sends data packets to a selected website. So if you go down and are unable to activate your PLB, SAR can begin from your last reported position.

You will likely need an auxiliary battery as Oudie Live can use up your phone battery, and yes, you need to be visible to a cell tower keeping in mind that higher up there's more visibility.