Pacemakers

Here's a solution for pacemakers & other low-draw, implanted medical devices that currently require surgery to replace batteries. Here's how an entry in Wikipedia puts it, "More recently, electronic quartz watches that are powered by arm movement have been developed. A weighted rotor turns a tiny electrical generator, charging a rechargeable battery or capacitor which powers the quartz movement. This automatic quartz arrangement provides the accuracy of quartz without the need to replace the battery or capacitor until it reaches the end of its life, which may be decades." While we're at it, this could be adapted to that expandable vertical rib developed for scoliosis patients.