There is few types/models of digital clocks available on the market.
- Vapor:
http://trailtech.net/vapor.html
- Acwell:
http://www.acewell-meter.com/
- Koso:
http://www.koso.com.tw/
You need to decide which one you need, and which option is the most important for you.
Some of us took clocks away and fited GPS Navi instead...