I think it would be useful. I presume you do it through postal code matching and people's postal codes would be matched with the MP's constituency. It could be used to alert an MP that a petition is being submitted by one of their constituents, but I don't think they should necessarily have to take that on board. They can see whether it's an issue that they believe is relevant or not.
On November 25th, 2014. See this statement in context.