According to 810, the Chiefs have a conference call around 4pm, to announce a free agent signing. I couldn't find anything online to support this, but they've mentioned it twice on the show.
Kevin Kietzman was speculating a WR, but really had no idea. They also said they don't expect it to be a big name, but more along the lines of what we've seen more recently.
I know this post doesn't have much info, but I just wanted to alert the AP family of the signing!