Android and iOS have /etc/hosts, which you can edit if you jailbreak. I dont know about Windows phone, they run something from Nokia. Some but not all Android

Android and iOS have /etc/hosts, which you can edit if you jailbreak. I dont know about Windows phone, they run something from Nokia. Some but not all Android devices permit you to install firmware you build yourself. Drivers for undocumented chips can be a problem You can block IPs at your firewall. I havent actually tried it but I understand you can install a VPS client so you could use a firewall even when you're at a wifi spot.