I'm looking for DNS software that can accomplish the following:

• Check health of all A records at set intervals
• If server is unresponsive after multiple successive checks, replace A record with a working server
• When a server is down, check it periodically. Once it's up, restore normal A records

Here's an equivalent I thought of:

• Run DNS servers with very low TTL (minutes)
• Use a cron job to periodically query all webservers
• Use sed to replace A records if need be, and then restart DNS server

I have a hard time believing there isn't already something that can accomplish the above. I'm not looking for a paid service, and I'm restricted to anything I can run with root access to a VPS. Any suggestions would be great. Thanks!