Mugen Extended Batteries are for smartphones. Actually they make them for smartphone users who are fed up with having to re-charge their handsets mid-day to keep up with their needs.
We’re talking a trade off, of course, between doubling your talk/standby time with a c.3200mAh battery (vs the 1500 or so you get as standard), against a large lump stuck to the back of your sleek, trendy fashion statement. Your call. Priced at around $80–96.00 or so, depending on model.
Mugen Power batteries have better performance (higher capacity) and reliability (longevity & safety) than other brands. The superior performance improves run time, often doubling that provided by the original brand replacement. The superior quality results in longer battery life and better protection of the powered device.