Interesting, never heard of it... so would this be added to the boil, or you talking about adding to the secondary and letting it soak up the garlic in there?
I think the secondary addition sounds like something that is feasible to me. You can use almost anything as long as it's sanitary, soak some garlic in vodka. Then maybe do a small batch of your beer to try it out. I took a class where they suggested separating into 1 gallon batches and trying out different flavoring techniques. You can always start with small amounts and add more.