Well, technically, there is a different -

1. Geocaching is primarily GPS based, and locating position with the help of satellites that provides longitude and latitude coordinates, and is very accurate.

   This Urban Tapestries is GSM/GPRS based, using a mobile phone, locating a position with the help of surrounding mobile phone base stations. The accuracy of a position is dependent on the site topology, and could be anywhere around 10-50 meters radius in urban context, for example.

Application wise, I think each serve slightly different purpose too -

1. Geocaching requires the seeker to actively seek the cache, and is primarily hobby based.

2. Urban Tapestries will probably do a information push when one is within a vincinity, and may not require one to actively seek it, except to give Urban Tapstries permission to push. This also means that it could be subscription based.

Theoretically, it could be possible to use geocaching caches(it's data) in GSM environment. However, the geocaching cache's seeker will probably have a harder time, as the cache will be very hard to find.