Sensicores are a perlon (like nylon) core string with a flatwound steel wrapping. I think they have been around for a while, but have never seemed to be as popular as other similar strings like Pirastro's Obligato or Evah Pirazzi. I learned about them from bassist Dave Roe. Dave does a lot off slapping and likes the fact that Sensicores have a smooth wrap and don't chew up his fingerboards like roundwound guts. Also, they aren't terribly expensive. I like the E&A better than the D&G. The E&A make a great combo with gut upper strings. (Dave Roe uses plain gut uppers)
Speaking of Dave Roe, here he is with my Acoustic Baby Bass, serial #1, back when Steve was just getting into this product line.
..Lyle