Befinitiv wrote an article describing his modification to turn a TS100 soldering iron into an oscilloscope:
As you can see in the video, you can use the soldering tip as your measurement probe. Coincidentally, a soldering iron has already a pretty good form factor for an oscilloscope. Here is a still picture of a UART waveform
See the full post on his blog.
Check out the video after the break.