California is a great state to own a motorcycle in. The traffic in San Francisco makes a bike the most efficient way to get around. But being new to the city, I don't always know where I am going. So I took a Magellan 1412 GPS unit and affixed it to my motorcycle. (You don't have to use the Magellan - any touch-screen GPS unit will work) Here's how I did it:
First I purchased a hard-wire conversion kit on eBay. This dropped the voltage from the battery's 12 volts down to the Magellan's 5 volts. The cost is $5 to $20.
Next, I hard-wired a lead from the rear tail light (this was the easiest place on my 2001 Ducati ST2; you may find other place to splice in from). The important thing is to make sure it's a power source that's only on when the ignition is on, and not on 100% of the time.
Lastly, I took a $1 metal spatula from the dollar store and sawed off the handle, leaving only the surface area of the spatula. I bent this in a vice to a 45 degree angle and strapped it on to the handlebars. I put velcro on the front of the spatula, and then velcro on the back of the GPS unit. And viola! I have a functioning GPS unit for waaaaay less than the cost of units made for motorcycles. Below is a video explaining the process.
One huge caveat: I only use this when I'm stopped, i.e., at an intersection. Paying visual attention to it while driving isn't recommended (to say the least). It also has audio prompts that work well in the city (too windy on the highway) but you could likely pick a unit with a bluetooth earpiece or headphone jack if you really wanted to.