Ask Slashdot: Smart firewalls for IoT

Ceaus writes: With the huge amount of challenges to protect our home networks from IoT cracking, I am thinking a smart firewall. It's a small box (the size of a RPi) with two ethernet ports which you put in front of your ISP router. This firewall is capable of detecting your IoT devices and block access to the internet, with only and exclusively allowing traffic for the associated mobile app (if there is one). All other outgoing IoT traffic is blocked (I don't want snooping eyes or internal botnet capability)
Once you've plugged in your new IoT toaster, you press the "Scan" button on the firewall and he does the rest for you.
Does such a firewall exist? Is this a possible Kickstarter project?
The idea is that this should be a cheap firewall targeted at home networks. I don't even know if this is a realistic project. I'd love to see some opinions on this.