After attending a couple of Quantified Self meetups, I was inspired to quantify various aspects of myself and my life. For example, I was wondering if I am breathing well while I sleep, since I have been waking up tired on occasion.
I bought the Contec CMS50-F oximeter from here.
The software that comes with the CMS50 could be more reliable and user-friendly, and only runs on Windows. I ended up spending a day reverse engineering the USB protocol and writing a Python program to acquire and graph the data. The software is on Gitorious.
Here are some of the charts you can get: