I have tried several wine preservation systems from injecting inert gasses to pumps of various kinds designed to remove air from a partially opened bottle. The goal of these systems is to add a couple of days of quality to the life of your wine. This is especially useful if you don't finish a bottle the day you open it.
I normally use the cork attachment on my Food Saver vacuum system to pull a partial vacuum. It works well, and remains my favorite. However, I have also tried various hand pumps to pull the vacuum. Vacu Vin works well, but one can never be sure it has worked until one squeezes the stopper for your next pour.
A few months ago I was in the Houston Wine Merchant (2646 South Shepherd Drive) and saw a new style of hand pump. It is made by Metrokane and called a V-Gauge. As usual with such pumps, one places a mechanical stopper into the bottle. Next, one moves a handle to pump the air from the bottle. Most hand operated vacuum systems employ this technique.
Where the V-Gauge differs is that there is a gauge on the stopper with a needle that moves from green zone to the red zone as the air is pumped out. When you are finished you have a visual indication that a vacuum has been created and, even more importantly, is holding.
Also, as an added bonus, there is a simple button on the top of the stopper. Pulling it up releases the vacuum, making it easy to remove the stopper and pour the wine.
This device seems well thought out. As the needle moves to indicate the removal of air, it gets harder and harder to pull the pump handle. Also, it is easier to move the needle into the vacuum range when the bottle is full than when it is only a third full. Finally, when the release button is pulled, the vacuum grip is relaxed. All this is as it should be if indeed a vacuum is being created. Air is the enemy of wine preservation, and I am convinced that air really is removed from the bottle by the V-Gauge.
In conclusion, the Metrokane V-Gauge system is well thought out. What makes it different--and better--is that the gauge allows one to know that a vacuum has been created and that the vacuum is holding. At a cost of about $20.00, this is a very worthwhile addition to the wine preservation arsenal.