Got a Harley? Got an iPhone? Download the GaugeFace app and you'll have a digital dash. The unit plugs into the ECU. It charges the phone and displays a speedometer, tach, engine temperature, signal indicators and what gear you're in. There are plans to add more gauges to the display in the future.
What models are supported?
Generally, all Harleys since about 2001 with EFI (Electronic Fuel Injection) based Delphi ECU's should work just fine. New 2011 Harley Softails are not yet supported as they have changed to a new HDLAN protocol and have a different data port connector.
Cost of the app and connectors is $250 Canadian.
There have been a lot of companies and individuals working to interface the iPhone and Android based smartphones to motorcycles and cars. I would expect to see a lot more of this in the near future.