DevExpress has a suite of controls for ASP.NET which include gauges. ASPxGauges Demos
I've recently used these in a project to display current information by doing asynch postbacks on timer tick, using their CallBackPanel (thier equivlent to an UpdatePanel).
Overall, the learning curve was not to steep. I would definitely recommend reading the documentation ASPxGauges Docs before jumping in. Design time support is available to create the controls, but is very tedious nonetheless.
Hope this helps.