So with all the background syncing, data transfer and what-not going on these days with cloud services - this app lets you use a hotspot like your phone but only allows the applications you decide to access your 3G or 4G data.
From the website:
TripMode automatically reduces your mobile data consumption when you use a mobile hotspot
Block unwanted traffic
Only apps that you’ve selected are allowed to access the Internet when TripMode is ON. The rest is blocked.
Save data automatically
TripMode activates itself on networks where you used it before. No need to fiddle in menus. It’s super easy.
Track your data usage
See how much data was used per app and per session, day, or month. Spot the data hungry apps.
BTW for android there are plenty of these apps for free if you have root - unsure though for those without root access
For windows a few alternatives like netlimiter are worth the investigation.