Mini Vacuum Speakers
These tiny speakers have a new vacuum technology that has to be heard to be believed. They have a rechargeble battery that can be charged from usb, a power adapter, or a solar charger. They can also be paired, playing two at a time to increase the effectiveness of you training.

Solar Chargers

These solar chargers have a battery big enough to charge several of the smaller units in the dark, once it has been fuilly charged. Built solid to withstand those areas that require solar power, this is a useful addition to any training technology used outside of the reaches of the power grid.