I actually made a champion concept with a similar ability because I thought it was an interesting idea.
Basically you could place a ward-like motion sensor that would alert the player if an enemy champion is within the range, but would not grant vision on it's own. While the 'trap' is triggered, it would allow the champion to fire ground targeted skill shots (sort of like Xerath's ultimate) into that region, regardless of their respective locations on the map.
The champion was actually incredibly complex, which I believe is the reason for it to not get any real attention (and the fact that my post was a huge wall of text, despite being formatted fairly well). The basic idea was that the champion was mediocre at damaging enemies who he had vision of, but would deal massive damage to enemies he did not have vision of. His kit included the ability to significantly extend his range and to essentially hinder his own vision (like how Rek'Sai does when burrowed.)