BoostyLink

This app is a companion to your Hybrid/Boosty enabled home router, and will boost the reliability of your home broadband connection by augmenting it with the cellular on your smartphone. For those gamers who can't tolerate any disruption, or for people working from home and their broadband needs to always stay up, this is an invaluable solution to always keep you online.
To get it to work there are a few simple steps:
Ensure that your home router supports the Hybrid/Boosty functionality. Contact your ISP to check if it is
Connect your smartphone to your home router's Wi-Fi connection as normal
Turn on the app and confirm you want your smartphone to work in tandem with your home router
That's it you're up and running!
When your home broadband goes down this app will seamlessly kick in as a failover connection and will keep your existing sessions up and your public IP address the same. As soon as your home broadband comes back on-line we'll stop using your mobile data. To ensure you never get any surprise bills you can specify a data cap, after which we stop using your cellular data.