Apple Watch vs FitBit / LIbre2 Question

So I'm torn between the Apple Watch, and a FitBit.

My biggest issue is my Libre 2 monitor.... it seems neither one will show me a continuous reading - or warn me when my blood sugar is really low - without my phone being with me.... which, defeats the purpose here as my phone isn't always with me.

Can someone talk to me like I'm 5 and let me know what version of a watch will do this, and if I have to do anything to get it to work. (It's my understanding the LIbre2 app isn't available for the watch).