Nokia Play 360 is a FAR better speaker for only a small bit more money, double the bass, double the battery life, auto shut down, NFC etc and almost the same size (thewirecutter.com)
The 500e evolves the principle even further, using the same size battery (24 - kWh lithium - ion) to generate 111 hp (4 hp more than Leaf). (wardsauto.com)
With the same size battery found in the Samsung Galaxy S3, the Nexus 4 should be able to manage a days usage without too much hassle. (t3.com)