I often run out of charge on my iPhone, especially when away from home. We've just spent 3 days in London and by the end of the day I've used my phone regularly - taking photos, looking at train app - all the things you do to make life easier - and consequently have no charge left on my phone. My brother showed me his phone case which had an in built charge - you charge it separately and when placed on phone (and switched on! I missed that step to begin with) you effectively have 2 batteries so twice the battery life! At under £10 it's brilliant - see link in side column.