Just What Does This Sign Mean?

Last week it was Blake Shelton lyrics I wondered about, but this week I encountered a new sign I can say I've never seen before-- and, oddly, don't know exactly what it means.

I saw this sign earlier Monday morning in the parking lot next to the old Lourdes school location, along 7th Ave and 2nd St NW. I'll use that lot every now and again, when I'm headed to the Dan Abraham Healthy Living Center, but I never noticed these signs before. There were several off them, along the first row of spaces facing 7th Ave.

"Cell phone waiting only"? I can honestly say I haven't the foggiest idea of what the sign might be getting at.

Is it a spot only cell phones can park?

Is it a spot you should park in if you're waiting for your cell phone to charge?

Or maybe it's a spot you park in while you're waiting for a very important call?

While I'm sure those aren't the actual reasons behind the sign, I will admit it's got me stumped. Do you know what it means?