for a wearable I think ESP8266(with a ble module) or esp32(wifi/ble on board) would be the “correct” way to go about it - then most likely connect it to a phone via BLE or just pure wifi.. perhaps mqtt to some elixir server..
(this is due to power/battery requirements..)
however I also assume you are in it to learn a thing or two, and perhaps elixir/nerves related stuff - so it all depends - what are looking to solve/learn?
for nerves you can start with a raspberry pi zero w - add a few sensors and a power bank and you are rolling..
BLE on nerves elixir is bluex GitHub - highmobility/bluex: Bluex is a Bluetooth Low Energy abstraction layer on top of the DBus/Bluez. · GitHub (much outdated it seems) or harald https://github.com/verypossible/harald (low level it seems) - so not sure of the BLE “story” on nerves - could be a bunch of hurt to get it working..
