Handheld bluetooth temperature

Projects General Guidance
1

Dear All,
Good day
I'm really new to Arduino projects.

I'm thinking about making a Handheld weather station with bluetooth connection to my android phone that alarms any drop or increase in temperature. (Micro SD card, 18650 rechargeable , Low power use , no screen values set by phone )

Any Advice on the components choices , I was thinking about Arduino Nano since it's small.
Could the Bluetooth XBee module only ??

Similar product :

Any Input would be great
Thanks

2

A Nano can't be such a good idea, I think a 3.3v Pro Mini would be a better one.

Could the Bluetooth XBee module only ??

Unintelligible. An bare HC-05 Bluetooth is entirely adequate and probably a lot cheaper.