It's been many years (and a profession change) but I'm pretty sure the RILOE and RILOE II that were linked to will work in any BIOS based computer just fine. It's not going to offer all the features, but they were just seen as standard video cards and some other devices to the system, along with using a normal PCI (not PCIe) slot.

http://webdevsys.com/lightsOut.htm has more info. Some people had success with remote power on as well, by hooking into the right cables inside their machine. About all you miss out on are Proliant specific features such as using the internal ribbon cable for Keyboard/Mouse instead of external PS/2 connectors. The boards were designed to go into Proliants prior to the 16/30 pin connector, hence the also broad non Compaq/HP support.

I wonder how many of the more advanced features work. For troubleshooting, the RILOE was awesome. It would video record any system crashes, allowing later replay. Windows bluescreen, Linux kernel panic, or a Netware abend, didn't matter.