|PbA (Lead Acid)||NiMH & NiCd||Li-ion & Li-Poly|
It's fairly old technology as has been used to provide power to deep space exploration like Voyager and Pioneer. They are also commonly used in pacemakers, Automatic Internal Defibrillators, and other implants. The misleading thing is that it IS radioactive, it uses radioisotopes and rely on the radioactive decay of the isotope. Beta emissions are fairly low emission and easy to shield, but I still think it might be a hard sell to people knowing they have a radioactive power supply. The space probes tend to use more dangerous isotopes like Plutonium Dioxide. It's safety really depends on the isotopes used. Energy capacity is huge, approximately 10,000,000 W-hr/kg versus 30 W-hr/kg for lead acid or 200 W-hr/kg for Lithium ion.