Ask Slashdot: Hardware for Headless Linux Boxes

Alan Hodgkinson asks: "I would like to setup a bunch of Linux boxes without keyboards and monitors. The systems must be accessable/controlable via their serial ports, including the ability to send them a hard reset. Sun Sparc hardware has this feature. You can remove the keyboard and the system will boot and send all its console output through the serial port. You can even reset the machine by sending a break to the serial port. Is there any hardware available for PCs that will provides this functionality? (And that works on a wide variety of PC hardware). ISPs must face this problem. What do they do? Tips anyone?"