Youtube user [npaltmp] hacked up a alphanumeric LCD from a defective answering machine, an ear clip pulse sensor from a stationary exercise bike and interfaced it with an Arduino “using a simple circuit which normalizes the photo-transistor’s output voltage and amplifies fluctuations”.

The Arduino senses rises and falls in voltage on one of its analog inputs and counts them as heartbeats. Motion is sensed with a crudely built vibrations sensor attached to my bed. It consists of a coiled thin wire pendulum which makes intermittent contact with a loop shaped electrode during vibrations. It is wired to the Arduino just like a button. Originally I had all heart beat events reported to a running desktop computer for logging, but I disliked this because it seemed silly to keeps a ~200 watt machine powered up for 8+ hours to collect only kilobytes of data. I reduced sampling rates, and made some other compromises in data collection, and now the sleep monitor stores data in the ATmega328’s 2kb of ram. When I turn on my computer in the morning, I can download the data with a C# application and have it stored to a comma separated value format file. CSV files load easily into Excel for analysis.

No code or Schematic is provided (some schematic can be found googling though)

Via [nopaltmp] on youtube