This is a massage tool with ribs or ridges that you roll the foot over. It was designed by a podiatrist. Many people find it helpful for plantar fasciitis and those feet that are tired at the end of the day.
Most Useful Resources:
Does the PediRoller massager really help?
Buy the PediRoller
Self Massage for Plantar Fasciitis (Plantar heel pain)
Foam rolling for plantar fasciitis
What does the science supporting foam rolling say?