Smartphone application show info about nearby Wi-Fi networks it finds, i.e. channel, SSID, MAC address of router, etc, except it IP addresses. Is it possible to discover IP addresses of nearby Wi-Fi networks without connecting to it?
No. To find out the IP addresses you'd have to be able to connect to the DHCP server that handles giving out the IP addresses for that subnet, get and IP address and a subnet mask, and then scan the subnet for active IPs. To do this, you'll have to be connected to the access point.