Patterns — mobile
How can a service effectively provide notice to a user who gave permission once but whose information is accessed repeatedly (perhaps even continuously) over a long period of time? Proactively notify the user after the time of consent that information is being tracked, stored or re-distributed.
Encryption with user-managed keys
Use encryption in such a way that the service provider cannot decrypt the user's information because the user manages the keys.
Active broadcast of presence
Users may actively choose to automatically provide updates when they want to share presence information, to increase both the relevance of, and control over, their sharing.
Provide an ambient notice (unobtrusive, non-modal) when location is being accessed to increase awareness of ongoing tracking.