Yes, agree that the definition would have to be pretty robust, but not so much on the "pilot can't land bit", after all modern aircraft have a range of devices which are there to help the pilot but do not mean that he/she are redundant. e.g.auto-thrust, auto-brakes, armed spoilers, TCAS and even autopilot itself to name just a few.
The new Airbuses are even equipped with a system which tells the pilot if he/she can complete the landing in the remaining runway length.
In terms of parameters, I would imagine that, put simply, the system would prevent the plane from rising or staying level once the thrust levels have been closed for say a second or longer and the altitude is below a certain level but the purpose of my question was more to explore whether such a system would be possible technologically rather than the precise parameters operationally.