For those with a more romantic bent comes a great project from instructables user 'ghostbust555'. Using an Ethernet-enabled Arduino board it determines the distance between the project and another person using an Android phone running a custom app. The project contains a laser-cut acrylic heart illuminated by bright LEDs - which increase their blink rate when the person with the Android phone comes closer.
When recreating your own beating distance heart or building a networked Arduino project, consider using our Freetronics EtherTen. Apart from being fully Arduino Uno-compatible, it has onboard Ethernet, microSD socket, full USB connection (no pesky FTDI cables needed) and supports optional Power-over-Ethernet: