Batteries that harvest energy from the nuclear decay of isotopes can produce very low levels of current and last for decades without needing to be replaced. A new version of the batteries, called betavoltaics, is being developed by an Ithaca, NY-based company and tested by Lockheed Martin. The batteries could potentially power electrical circuits that protect military planes and missiles from tampering by destroying information stored in the systems, or by sending out a warning signal to a military center. The batteries are expected to last for 25 years. The company, called Widetronix, is also working with medical-device makers to develop batteries that could last decades for implantable medical devices.