Trip Ward Concept

I was reading another post that consisted on riot and one guy talking about wards, and their potential functions. I figured I'd pitch a simple concept, see what people think.

I would like to see a trip ward with the following characteristic. Might make a good champion ability if you just add damage.

-I suppose it wold be an medium size line. About half as wide as the river, and invisible to enemies. -Marker on the map to indicate where it's placed. -Grants no vision. -Map visible ping when an enemy walks over it. 10 second cool down. -Last longer than standard ward. -Upgrade: Two trip wards. Slightly wider.

You wouldn't be able to see who is coming or how many, but it would be hard to miss someone tripping it. I'm pretty surprised Riot hasn't used anything like a trip wire in their champion kits.