No, not a Bum Trumpet ;)
Why would you want this? Well, in a modern world you don't as DHCP clients will configure routing correctly and have more bang for your bug with autoconfiguration. So what's the use of it? The answer is found in the new buzz-word of the moment - virtualization. To get a virtual host to talk to the host and out into the internet you have to setup some kind of bridge between the two. A Proxy ARP daemon takes away the need for this. Here's an example of it's use.
Anyway, version 1.0 has been rushed out the door. Tested on Linux, FreeBSD and NetBSD. Linux does have an in-kernel Proxy ARP daemon, but I think the userland is a better place for it. You can find it right away in pkgsrc-wip with an rc script.