Plugin that will allow client to check-in on Google Maps

Hi there,

I have a plumber client who would like to check-in their status whenever they arrive at a client's premises (the legalaties of that are being worked out at the moment).

Can you recommend a plugin that will allow this client to use their smartphone (iphone) or tablet (ipad) to quickly press a "check-in" button and which then publishes this on a map that is embedded on the website?