There are a few select times when having a stylus for your iPhone can come in handy. For me, I sometimes want to practice writing Chinese characters on my iPhone, and using my finger seems a silly way to do that. Another good instance is if you like to draw, it's often more natural to use a pen than your finger (unless you are in pre-school of course).
I looked around a bit and found that you can buy a stylus for your iPhone if you are so inclined. However, but being the frugal, I-wanna-make-it-myself guy, I decided to build my own. Plus, the pre-made versions look like they are built for a small foot print, and I want a pen sized stylus.
To make one is quite simple, and you probably have all the parts laying around your house. Here are the basic instructions and required parts.
The part I changed was I swapped out the exacto-knife and just used a proper pen. If you do that too, make sure it has a pretty good diameter. I started out with a .635 centimetre (1/4 inch) diameter pen base and it didn't work. Using one about .9525 centimetre (3/8 inch) worked perfectly.
Here is a movie showing it working. The response is quite good. I was filming it at an odd angle so it looks like it's a bit sketchy, but if you use it properly and press down with a bit of force, it works really well.