Heart rate monitoring

I'm not sure if this should be posted as "Emerging Drake" or as "Occlusion Culling"... It fits in both categories. But since I might create more projects regarding heart rate monitoring, I decided to post it here.

My mother recently gave me a heart rate monitor, which has the option of uploading the data to a website. Fortunately there are various ways of retrieving the data yourself, and processing it. I wrote a little script, that, when provided with an url= parameter (try "cashimor.xml") plots the data from the file. I'm not sure if this is a generic file format, or whether it only applies to the Timex Ironman with data xchanger. Anyway, here is the first graph:



It shows me having breakfast (it seems reading books causes my heart rate to drop below 65) and then, about 14 minutes after the start of the measurements, carrying the bike downstairs and cycling to work. At 27 minutes in you can see the bridge over the US-85, causing my heart rate to go up to 135, and then down to 100 as I glide down the other side and wait for the traffic light. At 34 minutes in you see the bridge over the US-101, which is longer, steeper, and more scary (I need to cross a lane of traffic). It goes down more gradually because the light was green. Near the end you see me climbing into the parking lot of Google. Here is the second graph:



It shows the part after the cycling, where I sit in my chair and code. There's a small peak when I went for tea (13 minutes in). And here is the third graph:



Where I cycle back. Since the most resources claim my ideal heart rate for exercise is 127, this looks pretty good.