Default [Q] Spoken ads within Android?

I''ve asked this question in the Nexus 5 subforum too, but I am actually not sure it has anything to do with the device, more with apps.

Twice in the last days, I have gotten a spoken add on my Nexus 5, running stock 4.4.2.

Message is something like:

"YOU HAVE WON A FREE APP, SHAKE YOUR PHONE NOW TO GET YOUR FREE APP"

Even putting it down or a slight hand tremble will throw me towards the market where I see an app. Nothing shocking, but I have no clue what app is doing this. The first time I think I was working in the Gmail app, second time I was in Kik. Does anyone know how I can track which app is doing this?