Not sure on the logistics around a criteria like this, but may be a great feature for the avoid planners or those on strict budgets and may want to avoid any CCA or anything similar debiting out of schedule!
Allows full control of when card payments can be made.
Two options to pick between, If app closed Freeze Card, or if Phone turned off, decline?
Not sure if anyone has suggested these, or I may just be making a stupid suggestion!
If you go to use your card when your phone is off or battery is dead or you lose or damage your phone the last thing you want is your card automatically locked
In the above scenario your life has ended and so your card may as well be dead, too. 
I get up most days before 8am and go to bed just after 2am, so I find my phone won’t last out all day and evening and goes flat every day needing a recharge afternoons
haha, fair comments.
Just wondered if was worth suggestions, one of the clients from work has put in new security method recently, where everytime I want to to access anything or change servers I have to approve via a phone app.
Just thought would suggest incase this would of been also useful with peoples monies!
Maybe secure the app if a sim card swapped?
Are you mad!! I would be even grumpier than normal with that amount of sleep 
At one point I worked 2 jobs, my main job 9am to 6pm and a nightshift job 9pm to 6am, then I did not get much sleep 
but that only lasted 3 months as one of the firms folded up
Ouch! Sounds tough!!
This is just technically impossible. Don’t have time to explain yet but it’s not possible to reliably know the ‘off’ state of a phone remotely, unless you’re willing to ‘ping’ it every X minutes which will melt its battery in no time (in addition to raising false-positives where no network coverage will be considered as ‘off’).
Cheers for explaining that 
Was all just an idea. Thank you!!