A wireless sensor network (WSN) is a wireless network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations. Wireless sensor networks are now used in many civilian application areas, including environment and habitat monitoring, healthcare applications, home automation, and traffic control. In addition to one or more sensors, each node in a sensor network is typically equipped with a radio transceiver or other wireless communications device, a small microcontroller, and an energy source, usually a battery. In contrast to the traditional sensor networks that are carefully planned and deployed to the predetermined positions, wireless sensor networks can be deployed in an ad-hoc manner. Of course, such deployment requires adequate communication protocols that are able to organize the network automatically, without the need for human intervention. Size and cost constraints on sensor nodes result in corresponding constraints on resources such as energy, memory, computational speed and bandwidth. In computer science and telecommunications, wireless sensor networks are an active research area with numerous workshops and conferences arranged each year. Various technologies can be used for communication between the different sensor nodes like Infrared, Radio Frequency (RF), Optical Communication (Laser) so here we discuss the scenario of use of Bluetooth in the Sensor Nodes. The main principles, applications and issues of Bluetooth based wireless sensor networks.