Something strange happening at tick over

[Timbollew]

So I sorted my problem with the speedo and changed my oil and filter. Took the bike for a blast today and all going well. I stopped for 5 to text a mate and as I was stopped the revs occasionally would drop from 1000 down to 500ish stay there a little then go back up. It was doing this on and off. I've never noticed it before do you think it could be something simple like plugs? Or I've seen a lot of you guys talking about the TPS, could he related?

I took a video on my phone so if it'll help could post a link and upload it to YouTube.

Cheers.