I think the exchange called Multisigna does exactly that, and Coinffeine should be similar as well.
They do seem to operate in the same spirit as the OP. I would like to see wallet apps designed with this feature someday. This isn't about a real security issue. This is about giving common folks an added layer of security they otherwise might not choose.
Bitcoin's multisignature has been talked a lot and Electrum has offered this function. But it seems most of bitcoiners still don't bother to switch to multisignature address. What is the problem?