My commute is a big one - I spend around 3hrs a day on trains. So it goes without saying that I tether a LOT in order for me to use the time productively. The unfortunate bi-product of this is that I use a considerable amount of data - I recently had to upgrade my phone to a 10Gb allowance per month.
Prior to my upgrade I was on a 4Gb monthly package and it was beginning to become a regular occurrence that I'd exceed it. However I simply couldn't work out where my data was being used - I don't stream music or videos and I'm usually very careful in downloading large files at home or at work. So this led me to search for a piece of software that could help me solve the issue. And after test driving various solutions, I discovered TripMode.
TripMode's genius is in its simplicity. It sits in your system tray and when you first connect to a wi-fi hotspot, it disallows wi-fi access to everything on your machine. To permit access to a piece of software all you have to do is tick a little box next to its name in a drop down list. And that's it. Tripmode remembers each wi-fi hotspot uniquely, so next time you connect to the hotspot it will remember the permissions that you previously gave.
Alongside this, TripMode also counts the data usage for each individual piece of software, so if it gets to the end of the month and you're wondering where your data was used up, you can see clearly and adjust accordingly.
TripMode does exactly what it says on the tin and at only $7.99 it's by far the best piece of commuting software that I've ever bought. Highly recommended.