A tennis ball against the wall or laying on the floor slowly rolling on it is cheap & simple..

If you have sore & tight muscles a digital IF stim is something I have found very helpful too.

this is the one I have had for 4 yrs or so now..
https://www.google.com/search?q=Digi...nit&gws_rd=ssl

great for any pain- low back, neck, shoulder, hip...