Seriously.. get cats. Mine sit nicely on my back when I lie on my front so I get a nice warm heatpad glow.... They will massage you (the claws can get a bit painful, but there are people who will pay good money for that sort of treatment) when they feel like it, and keep you fed (providing you like mice). They'll also snuggle up against you in bed, thus keeping you to the unorthodox but convenient (for them) R shape.

LTS ~ cat owned by 3 and not had a bad back for years. Manitas is a cat repellant and is suffering from a bad back.... you do the equations!