The folks at OpenSource RF have launched RFduino on Kickstarter, one of the smallest Arduino-compatible microcontrollers around, and it even has Bluetooth 4.0 LE built in.
This looks like a wonderful platform for prototyping Internet of Things sensor-based applications where your smartphone serves as the hub or brain. They have several imaginative projects outlined on their Kickstarter page, including proximity sensors, plant monitors, door sensors and button press detectors.
