This project is powered by the awesome BeagleBoard and the Arduino microcontroller platform. It is a location-aware (GPS) weather station that collects data about the ambient temperature, humidity, gas/pollutants levels using sensors connected to the Arduino in that lat+long and tweets them. The form factor would allow you to keep it mobile since it would be powered by batteries. So, it can collect and log data (using an SD Card) and tweet using wifi while on the move. Further features could include using a GPRS module to increase coverage. You can use the logged data to even plot graphs, etc. It would also contain a touchscreen display for the UI.