I’d like to see the amount of time spent on the app and web pages together. The stats page has the coloured boxes and number of reviews per day but I was wondering if there was an add-on that could let me see the time spent each day aswell. Thanks
In the same Stats page – on the Reviews graph, tick the “Time” checkbox.
This adds up the time spent on the front and back of a card, up to the Maximum answer seconds you have set, for each time you see each card.
Thanks so much 
is there a way to change the time period on that part to see the total time for a week or something?
No, the options are 1m, 3m, 1y, as shown in the picture – and all, if you look at your all history stats.