I'm running HackMaster new edition on Roll20. The combat system uses a count-up system during combat with the GM calling out each second and players taking action accordingly. Hopefully Roll20 will eventually have some sort of floating count-up window but until then I came up with this work around.
I found this virtual scoreboard at <a href="http://www.javascoreboard.com" rel="nofollow">http://www.javascoreboard.com</a>. Running it on a second monitor I use Camtwist's desktop+ feature (lets you select a portion of your screen to broadcast). I select one of the scoreboard panels. Then during combat I simply switch from my webcam to camtwist. So instead of seeing my ugly mug -- the players see the "count" instead.
Hopefully someone else finds this useful.