The Goofball Proximity Surveyor (護符・ポジショニング・システム,Gofu Pojishoningu Shisutemu, Positioning System Charm), commonly abbreviated to G.P.S., is an Amanohokosaka Clan charm that was modified by Mei Amanohokosaka. The charm has two abilities, the first is to help Mei locate a person that the charm is attached to; the second is to temporarily disable the Drive of the person it is attached to. The charms were apparently 'very rare'.
Mei first attached the charm onto Tōya Kagari so she could monitor his location and attempt to prevent the power of the Black Beast appearing; however, the power of the Beast was too great and the charm flew off when the power awoke. Mei also used the charm again on Acht so that she and Kuon Glamred Stroheim could use magic against the Ten Sage. There are no more of the charms left as the last one was used on Acht.