Does anyone know anything about these solar chargers, if they're useful or are worth it? I seems that (if I'm not mistaken---famous last words) a lot of them all seem to be made by one Chinese manufacturer, then sold on various sites for $25-$40 or so a piece. Are they worth the money for the convenience factor, or does anyone have one they could share info on? Thanks. Analog free since 7/18/11 and have saved a ton of money, don't reek, and can now get from Point A to Point B without passing out.....not counting the YATL (Years Added To Lifespan!!!!)