MKS EZY removable SPDs (or flats) ftw!
The link Adrian posted covers the Samsonite thing quite well.
I found these dangerous and unreiable
Maybe because of big feet?
About two weeks after I purchased the SPD version,the small plastic "safety collar" disappeared
After that any attempt to disengage would remove the pedal from the bike rather than the shoe from the pedal.
Trying to put down a foot in traffic with a pedal attached is something you only attempt a couple of times
Then having to dismount and hobble to the side of the road, remove shoe, detach pedal, reattach pedal to bike and continue is also time consuming
They may have improved, or it may just have been big feet, but I would recommend caution in their use