You can revoke all pairing trusts (on ios8, at least) with: Settings > General > Reset > Reset Location & Privacy AFAIK there is no UI for individual pairin

You can revoke all pairing trusts (on ios8, at least) with: Settings > General > Reset > Reset Location & Privacy AFAIK there is no UI for individual pairing management, but I think the full reset is completely safe/non-destructive otherwise -- just re-pair on the machines you do trust, and everything continues as usual without data loss or huge resync, etc.