My chiropractor uses something similar, called the Jeanie Rub Massager.
http://www.protherapysupplies.com/pd_jeanie.cfm
He runs it over my back after every adjustment. It feels quite soothing.
One of my colleagues is both a PTA & an MT. She used this frequently in the physical therapy office, so she added it to her menu of services in her massage office ($15 for 15 minutes). She has a very busy practice, but not one client was interested in being massaged by a machine. After a year, she gave up & brought it home. Now, occasionally, she & her husband use it on each other. (When they're too tired to give each other a regular massage).