I just got a set of these:
Shimano Saint MX80 pedals with a pair of Five Ten Freerider shoes.... The tread on the shoes lock onto the pins on the pedals and it feels like your feet are glued to the pedals. There is almost no slippage. Yet it is easy to "unclip"...
I don't use clipless because, on the trails I ride on, you simply have to expect the unexpected: dogs and kids jumping in front of you, squirrels, deer and so on. I simply don't want the risk of falling from not having time to unclip after coming to an unexpected emergency stop.
I tried them for the first time yesterday and I love 'em! The shoes stick to the pedals like clipless but release (almost) like regular platform pedals... I did have one spot where I had to put a foot down very quickly and I almost met the membership criteria for Club Tombay -- but I was able to get my foot off of the pedal quickly enough...
They're not going to let you 'pull' on the pedals -- but they do seem to provide a similar level of lateral attachment.
And, oh yes! You can actually walk in the shoes!
I love 'em!