In 1x07 - The War Prayer - there was a plot to kill all the ambassadors. The would be assailants were to use devices thought could be described as personal cloaking devices.
Kinda makes one wonder what happened to them. Did Sinclair give them back or did he keep them?
Also kinda makes one wonder... if Sinclair / Sheridan had held on to them, how might they have been able to use them?
Maybe Marcus and Franklin could have used them to go to Mars on a nicer ship. Maybe they could have been used to discretely infiltrate the facility where Sheridan was being interrogated. Garibaldi could have also used them on the Drazi homeworld (in the episode where he found that the Centauri ships were being remotely controlled).
It seems unlikely that they would have been effective against first ones.