The Philips CD-i system has pretty much been unemulated this far, but now things is changing. A new emulator has been released, simply named 'CD-i Emulator', unfortunally the emulator isn't free, but there's a time-limited demo to try.
The CD-i emulator program (cdiemu) provides a fairly complete emulation of the hardware of an actual physical CD-i player.
The time-limited edition emulates for at most three minutes between CD-i player resets and does not support permanent saving of NVRAM data such as game highscores and other CD-i title settings. The unlimited edition does not have these restrictions.
In order to actually run CD-i software, the emulator needs copies of the CD-i system ROMs. These ROMs are copyrighted and cannot be freely redistributed, but you can easily obtain them via the serial port of a physical CD-i player using the provided CD-i Link program.
Head over to the official site for more information and the download.