Nothing “handy”, but if you’re PHP-aware you can set up your own PHP compilation and use the “browscap” .ini setting in conjunction with the “get_browser” function in PHP. Provided your have an up-to-date browscap file, it’s quite efficient in regards to redirecting the appropriate bots to the appropriate place (also helps in adjusting for the inadequacies in MSIE’s CSS 2 implementation). Feel free to send me a private message if you’d like a copy of the browscap file I’m using.
Another way to do this is using IP/DNS lookups to blacklist specific IPs and ranges of IPs, but that’s a much more complex method.
Note that many bots will honor a “Robots” meta tag, but not all.