I think the answer is "Yes, it can be done, but you are going to have to work for it." The setup that worked with previous Pentax models was the Nikon version of the RF-603, but with the (Canon) C1 cable, which has 2.5mm connectors on both ends. You are either going to need a 2.5mm-3.5mm adapter, or a different cable (see thread linked below for discussion of the adapter). So far as I know, YongNuo does not make a 2.5-3.5mm cable. I have seen shutter cables on eBay with a 2.5 on one end, and a 3.5 on the other, but the right angle plug is on the 2.5mm end (the brand is Vello). I can't say whether they will work with the K-70. Good luck!
About the wired remote control. - PentaxForums.com