While a vacuum system isn't 100% reliable, I'm convinced it's still more reliable than a simple bubble check. For two reasons: (1) if you see bubbles, you already have some water entering the housing, and your camera might already be ruined. The vacuum system will warn before any damage is done! (2) if the leak is so small that even the vacuum system can't detect it, then I'm pretty sure you won't see any bubbles either!
Why would anyone wants to introduce flashing and blinking lights or monitor the partial vacuum inside. Just use it and forget it. That is best in my books. The valve does not even need to be fussed over. Just normal rise with the housing and it will work over and over again.
I think the leds (or a gauge) are essential! How else do you know there is no leak? If you don't have any means to check the vacuum before entering the water, you also don't know if there is a leak.
This probably saved my camera a while ago. I had vacuumed the system at home, and when I arrived at the dive spot, the Hugycheck showed a flashing red light. Upon closer inspection, the housing had completely de-pressurized again, which means a significant leak. Without that blinking red light, I would have entered the water without knowing anything and flooding the camera!