On May 15, 2014 MSI presented a technical paper at the Joint Armaments Forum, held in Phoenix, Arizona. The paper was titled Energy Harvesting IC for Illuminating Sights. This paper features the MSRFIF the Radio Frequency Interface Front End, a standard product IC from MSI. Here is the technical abstract from that paper:

One constant concern with newer optics on small arms is the need for batteries. Eliminating the batteries would increase the reliability of the system. Energy harvesting techniques would appear to be the best solution to removing the batteries. There are a number of energy harvesting products on the market. However, the Mixed Signal Radio Frequency Interface Front end is one of the few standard products that can work from low frequencies (60 Hz or less) up to 250 MHz. For eliminating batteries, a piezoelectric wafer provides a voltage that the MSRFIF's charge pump converts to a steady DC. Power output is limited by the amount of vibration the piezoelectric wafer generates. However, powering efficient LEDS is easily done with a minimum amount of vibration. This paper will present power output values and charge pump efficiency of this standard product.

This paper shows the MSRFIF powering low power LEDS to provide an illuminated red dot.

Here is the complete paper in PDF format.