Low energy consumption is just one of the major improvements of v4.0 over the v3.0. The new standard adds a low-power specification for transmitting small bursts of data over short ranges, and also includes the high-speed data transfer capabilities introduced with Bluetooth v3.0, which allows devices to jump on Wi-Fi 802.11 networks to transfer data at up to 25M bps (bits per second).
The upcoming Bluetooth version will be optimized for low power battery operation which will help the technology to conquer new markets such as health care, fitness and sports where devices require low power and low cost wireless connectivity.
Lower power consumption will also allow the technology to be used in way smaller products than before such as tiny coin-cell battery powered devices and sensors. According to the Bluetooth SIG, thanks to the decreased demand for power, products will be able to run for years on standard coin-cell batteries.
The other improvements brought to Bluetooth by v4.0 include low cost, multi-vendor interoperability and enhanced range.
The Official Bluetooth® Technology Info Site