I use the tradingview one  

 I use Bitcoin timechain widgets 

 Why would you need an app for reminding you
1 BTC = 1 BTC

You could set up a price alert on daily alarm of the same 

 Everyone has their own choice, however, he was asking this not for me but for one of my friends. 

 I was joking.
Price alerts, price widgets are all the rage when first start accumulating bitcoin.
We’ve all been there.
Overtime that goes away for most holders  

 I found a kraken widget in the app store 

 Bitcoin ticker 

 like this?
simple crypto widget
 https://image.nostr.build/2cc2a3b804b1e09173e46b2d06b0ac965eea8903134d3b381f09696ad4fca3d3.jpg 

 yes link  

 there's trillions - and lot's of free APIs for prices - make your own with android studio... get into programming with your own use case 😃 

 https://play.google.com/store/apps/details?id=com.currency.exchange.widgetscrypto