There was a whole thread about this and someone suggested Nancy's Notions Seam Ripper. I searched and found something similar
http://www.ebay.com/itm/Qripper-Quic...item3ce13cccf4
I wondered if a mustache trimmer might work the same, as many suggest, but think it would not have that guide to glide along the bottom.
I asked DH to check it out. Consensus is, the trimmer will expose your fabric to the teeth but the Quick Ripper seems to avoid that.