I use a iOS VPN app called Speedify, that simultaneously bonds wifi/cellular channels into a single channel, ostensibly for speed sake. It seems to handle situ

I use a iOS VPN app called Speedify, that simultaneously bonds wifi/cellular channels into a single channel, ostensibly for speed sake. It seems to handle situations where either wifi or cellular is flakey, and even has a redundant mode, where all traffic is sent via both channels simultaneously. Redundant mode is not fast, but it is rock solid reliable. I use it if I want to make sure I don't drop a VOIP call.