Probably the best tool to use for this sort of application would be FlightClub, developed by Declan Murphy. Launches have estimated trajectory data which the developer ingests into the system prior to launch to produce a viable simulation of the rocket's flight path. Post-launch completion, the developer then adjusts the trajectory to match the actual values (as shown on webcasts). You can opt to track these launches in "realtime" by following along with the launch.
Simulation of the CRS-9 launch in FlightClub
This data is overlaid onto Cesium, a WebGL-based 3D earth viewing application, alongside mission "vitals" such as velocity, altitude, downrange distance, and more.
Here is an example of Flight Club simulating the SpaceX CRS-9 resupply mission to the International Space Station.
Full disclosure: I am friends with the developer of this application.