SPD's are the way to go. I have eggbeaters and have a pair of mountain shoes and a pair of skate-style shoes that I can walk in without the cleat scratching floors. It's easy to clip in and out because they're double sided pedals. Also, if I want don't want to clip in I don't have to. With mountain shoes and (especially) those skate-style shoes I have, my feet won't slip off even if I'm not clipped in.
The shoes I have are something like these:
http://www.jensonusa.com/!9!44o5KFMU...FY1DMgodenIAog