Recently I finally had the opportunity to confirm the results of my research, as I have lent me a "GP-1" from an acquaintance.
Both devices are externally almost identical. The "GEO One 'is however slightly larger and has a different port for the remote cord: During the" GP-1 "the same socket as the Nikon D5000 or D90 is present, has the" GEO One' a socket for a plug (2.5mm). The matching Kabelfernauslöser is included directly in the delivery of "GEO One '. Owner of a D5000 or D90 can connect an existing wired remote release to the "GP-1". Who but a Nikon DSLR has 10-pin connector, requires either an additional Kabelfernauslöser or a Y-adapter to use their 10-pin Remote Cord along with the "GP-1" can.
A star deduction receives the "GP-1" from me for all defects which he has in common with the "GEO One '. I do not want to repeat this list here.
The second star I draw from (not Kabelfernauslöser) and the higher price for the lower supply. The imprint "Nikon" justifies this in any way.
Nevertheless, it is noted that the "GP-1" of course not always bad product. The build quality is very good (albeit plastic) and he does exactly what he should. The speed and accuracy of position determination are for a GPS device in order.
Those who want the same performance at a significantly lower price, go by "GEO One" definitely better. Who on the other hand emphasizes the company logo, just have to pay more.
A genuine alternative to both devices is, for example, the "Solmeta N1". It is priced approximately at the center, however, has its own battery (not drawn to the camera), and "remembers" the last position if the GPS signal drops out. Unfortunately the Solmeta N1 not available on Amazon.