There are loads of ways to hunt down an IP address. Patting yourself on the back because you know of an android app is silly. I would check the DHCP leases on the router, for one. Maybe check the ARP table ("arp -a" in CMD) after a ping flood in case of statics. If you use a Mikrotik or other router that has an IP scan tool(Ping Flood) integrated, viola. Use 1 of the "137 analyzers you can download for free and get the crappy adds". What do you do when it doesn't show up on your app?

This location used to be about helping people but now it seems to be a place for specialists to bash on the questioners.