Bose Soundlink Wireless speaker
Following many months of looking and testing, I bought one of these a month ago to use with my iPad and iPhone and it's fantastic. Sound quality is really good and it's much louder than it's size would suggest, due to it containing 4 drivers and twin opposing sub units, within its diminutive case. Best of all, it's rechargeable and lasts for at least 8 hours on one charge. The software is upgradeable and the battery can be user replaced when necessary.
There are two models, which are essentially the same apart from their looks. I bought the more expensive leather and chrome metal model, which is £50 more than the cheaper £250 model, which sports painted metal parts and a nylon cover. Both come with a wall charger and an optional audio input lead.