Once I gut a bunch of phone numbers in my Notebarn notepad, I started getting frustrated that I couldn't dial a phone number in a note just by viewing the note and clicking on the number. So I've updated the app to include this capability.
If you want this feature, and don't want to read any more geek ramblings, you can go right to the project page and download the app.
I missed this feature acutely because I used to use a Blackberry. On the Blackberry, whenever you come across an email address, URL, or phone number, the device recognizes the format of the text and creates a sort of smart tag. The trackwheel menu gets new tasks related to the data. If you move the cursor over a phone number, the wheel menu will include Call, Send SMS, and, if the number is recognized as matching someone in your address book, clever things like "Send an email to [name]", "Invite to meeting", etc.
It's not accidental that most Blackberry apps support this functionality: the folks at RIM supply classes in their platform API (net.rim.device.api.ui.component.ActiveRichTextField and net.rim.device.api.ui.component.ActiveAutoTextEditField to be specific) that do pretty much all the work for you. Use these classes, and you get this functionality for free.
Despite many strengths relative to the Blackberry platform, the .Net Compact Framework on Windows does not include such a class (at least as of 2.0).
Making this kind of an implementation harder, the Smartphone version of a multiline textbox has a "clever feature": In order to allow multiline textboxes to fit nicely onto a small screen, play nice with directional tabbing, and still accept a lot of text, they have two states. The base state shows one line of text and a little "expand" triangle. You can edit the text, the control responds to events, etc. If you click "Enter", triggering the expansion, the textbox switches into a fullscreen state where you can put in all the text you like.
The problem is that in fullscreen mode the component does not respond to all of its events (it doesn't even fire an event when switching modes), making it very hard to do context-sensitive stuff, such as "look at where the cursor is, extract the nearby phone number, and allow the user to dial it." Which is what I really wanted to do.
I implemented two workarounds instead. When notebarn finds one phone number in the note (using a RegEx that looks like a U.S. number), it adds a "Dial 415-555-1212" command to the main app menu. If there are multiple numbers, it opens a new window with a list showing each number and some of the context around it (so you can tell which number is which). Pick the one you want, and click to dial.