A mobile phone is always with us. It has information about our location, it contains a lot of data about ourselves, such as pictures, music, the phonebook with the list of our friends, etc. Adding external sensors is also possible. We can connect external Bluetooth devices and add for example, a GPS device, sensors to measure the temperature, to misure our heart-bit, etc. The range of applications and the study that can be done using this platform are infinite and it is possible right now, not in the future.

I just would like to highlight one nice application, BeTelGeuse, developed at the Helsinki Institute for Information Technology (HIIT).
With this application is possible to add a GPS device, a ECG monitor, and many other sensors. It is written in Java and the source code is available. A very good work!