geocaching is hiding and locating containers at specific geographic coordinates using GPS.
Besides the checkin information, I would also suggest another property which indicates whether you have found or did not find the log. Something like p-geocache-log-type where value is either 'found' or 'not-found'. With this property, we can also explicitly set a post to 'geocache' instead of a checkin only.
Kristof De Jaeger is currently exploring this with Indigenous for Andoid which has a Geocache form posting found geoaches on his site at https://realize.be/geocaching. Minimal context is also parsed from the geocaching.com site and wrapped into 'u-geocache-of'. The data for the checkin comes in by passing all info into the Geo URI, see https://indieweb.org/Micropub-extensions#Location_checkin_information
View source and look into the noscript to see markup.
Parsed by pin13.net: http://pin13.net/mf2/?url=https%3A%2F%2Frealize.be%2Fcache%2F1344
Notice the proposed 'geocache-log-type' property parsed there.
PESOS to WordPress
Dan Q has implemented a WordPress plugin that performs manually-initiated PESOS from a variety of geocaching websites including Geocaching.com and opencache.uk and is selfdogfooding it on danq.me: blog post | source code