Matt Mets writes:

Being a console junky, I am always looking for ways to improve my experience at the terminal. One thing that is is dire need of improvement is the console bell. You know, the really annoying beeping sound that occurs when you pressed the wrong key, that you immediately disable when setting up a new computer. Unfortunately, the bell really does provide a useful service: that of allowing the system to notify you when you need to fix your input. It is possible to turn on a ‘visible bell,’ which inverts the foreground and background colors of the console. In practice, though, I find this almost as annoying as the bell, and disable it as well. So what else can we try? It occurred to me that there is an obvious solution: haptic feedback! The only trouble is, I don’t know of many keyboards that have a vibrating motor built in. Of course, this is an easy thing for a DIYer to fix.

So Matt installed a vibrating motor in his keyboard (put in place of the Scroll Lock LED), and modified his Xterm to get the desired result. Code and schematic included.