I've always been a bit resistant to apps, I think because when my kids were tiny I lost my phone twice in quick succession and was always worried about the security of banking apps and others which hold personal data.
However, I have finally started to embrace them and would love to know which ones you use, especially if they help you to be more organised, calm and productive.
Mine would be:
Banking app: resisted this for so long but it's soooo convenient. Child's music teacher needs paying? DONE. Owe friend money for something? DONE. Need to check balance and so not feel guilty and stressed by not knowing how much money is left in account? DONE DONE DONE DONE
Tesco: since I've been back at work full time, I get a delivery every couple of weeks. The app makes it really easy to book my slots well in advance and add things to the basket as and when I think of them
Goodreads: mainly use this to track recommendations from the paper, MNers and RL friends, so I always have an idea of which books are worth seeking out in the library or kindle sale (or a real bookshop on the odd occasion that I am lucky enough to visit :) )
Period tracker: I use Clue. Keeps me on top of dates and finally proved that my periods ARE a bit wonky, but not enough to worry about. Reassuring that I would spot a change in my usual pattern if it happened.
Evernote: used for meal planning, brain storming and other times when I need to get something written down. Best thing is you can access it from the browser so I can look at it on my work laptop without needing my phone.
Birdnet: downloaded this during the big lockdown in the Spring. Record a bird song and it shazams it for you and tells you what you are listening to. Some lovely "spots" while out walking (and a zillion robins in the garden)