I know that some modern iOS devices actually require a specific voltage across the data lines to tell the device what wattage charger it's using. In that situat

I know that some modern iOS devices actually require a specific voltage across the data lines to tell the device what wattage charger it's using. In that situation you would have to add a couple of resistors to the charging cable between the voltage and data pins, which definitely makes it a lot more difficult for most people. You might find the following interesting: http://www.ladyada.net/make/mintyboost/icharge.html http://www.ladyada.net/make/mintyboost/icharge.html