(covers information from several alternate timelines)
A site-to-site transporter was a portable device that used transporter technology to allow the user to beam from one location to another without the use of a transporter pad. They were typically small hand-held devices or miniature models that could be worn on clothing, and were able to transport themselves along with the payload.
In 2372, in an alternate timeline, Tom Paris had acquired a hand-held site-to-site transporter. He and Harry Kim used the device to transport from a San Francisco street to Harry's office at Starfleet Headquarters and from the office to the Earth Spacedock. This type of transporter beamed itself along with the transported personnel. (VOY: "Non Sequitur")
In 2375, the Borg drone One developed internal transporter nodes based on the 29th century mobile emitter technology. These implants could be utilized as a personal portable site-to-site transporter. (VOY: "Drone")
In 2379, emergency transport units, a type of miniature portable transporter technology, had been developed by Starfleet. They were designed to provide a single one-direction transport for one individual. During the Battle of the Bassen Rift, Jean-Luc Picard beamed from the Scimitar to the USS Enterprise-E using such a device. (Star Trek Nemesis)