Connecting the real world to R with an Arduino

If connecting data to the real world is the next sexy job, then how do I do this? And how do I connect the real world to R? It can be done as Matt Shottwell showed with his home made ECG and a patched version of R at useR! 2011. However, there are other options as well and here I will use an Arduino. The Arduino is an open-source electronics prototyping platform.