You could use a Pyronix enforcer, it has two wired zone inputs (if you don't need to wire the external bell box) - note if you use the two wired inputs and want an external bell this would have to be wireless
It has wireless fobs / and or prox tokens & is fairly simple to use
Or another suggestion would be a texecom 12W (or similar) , fairly similar to the enforcer (probably better IMHO) it has at least 4 wired zones, it is wireless capable for expansion, has wireless fobs / prox tokens
Hope the above helps