WowAce

*Latency
Displays the amount of time spent between cast send and start events, in the form of a bar at the end of your casting bar, with optional text that displays the actual duration of the lag. This helps in canceling casts when they will not actually be interrupted, especially for users with consistently high pings.

Most CastBar and other UnitFrames support this, should be easy to add and has a major influence for casters being able to see their latency.

I was just about to request a latency feature for your castbar as well in the form of a bar indication as well as small text indicating actual numerical latency within that bar. Example implementation can be found in Quartz, Pitbull 4 also added this. Help casters greatly to know when to interrupt their casts and/or begin casting their next spell for optimum casting efficiency. This new AG_UnitFrames is coming along well!