You are correct in both cases, that there is a duplicate IP address finder in UDT and that you can set an alert to find them based on SYSLOG messages.
However, in BOTH cases I don't believe it will accomplish what sja is asking about. Both UDT and syslog will tell you if there are duplicate IP's on a given LAN segment. He is looking for duplicate IP's in his configs, specifically loopback or interface IP's. Neither of these cases will be found by UDT or syslog, but have a good chance of being found by the query I posted.
So, while you are right that you can find duplicate IP's using both of those methods, I don't think it will help with what is being asked for in this particular instance...