In developing nations, the ability to provide reliable power to some locations is a challenge. And in areas where people live away from cities, it is pretty much impossible to get electricity to them for providing light at night. You can imagine how hard it would be doing things in the dark like preparing food or putting kids to bed. The only solutions require non-standard methods, such as solar panels, but they have fairly high costs. Providing something at a much lower cost would provide light for so many without it.
DeciWatt.org is an organization behind the GravityLight which is planned to cost $5 and provide them to developing countries where electricity in some locations does not exist. What the final cost will be is an unknown, but will not be much higher than the current goals. It is estimated it will take someone who buys one of these about 3 months to pay for one.
The concept is simple to provide light using gravity. If you have seen the old Grandfather clocks that have weights to keep the time, it is the same basic concept. You put sand, dirt or rocks in the bags and hang them from the device and the weight is converted into energy which can provide a small light for up to 30 minutes. That is all there is to this.
This is another of the Crowd sourcing ideas which you can view on Indiegog where they had a goal of $55,000 and raised $399,590. You will get a great understanding of what they want to accomplish with this. This is one of the many things which can help individuals in areas with no electricity have some of what so many of us have taken for granted.