This is Dutch designer Anouk Wipprecht's Spider Dress. It monitors the wearer's surroundings and respiration, and extends its legs if their breathing rate increases or somebody comes too close. Not a bad idea. Also, just wildly waving a steak knife around. It seems to work for this guy I've seen at the bus stop.
Keep going for a short video of the dress in action.
Thanks to Rebecca F, who agrees personal space is important and you should respect it (or risk getting stabbed).