Wristband project- functions to include; Reminder (vibrate at set intervals), and vibrate upon bluet

Hi everyone,

I'm very new to arduino, and am not sure of the best way to approach my project. It's probably a bit advanced for me at this stage, but i'd like to have a go at it anyway.

I want to create a wristband device that can be set to vibrate multiple times in the day, example; every hour or every 20 minutes. and also have it vibrate in the morning via a mobile app (the app being another part of the project)

My first question is, would it be easier to just buy an existing "fitbit" type piece of hardware and write a simple app to control it to control it? or even get a bluetooth headset and replace the microphone/speaker with a vibrating motor? I'm not familiar with the rights and legal issues involved with creating apps for existing products... it's for personal use, for now anyway.

Second question; if the first option isn't a good idea can anyone recommend a suitable bluetooth module for this project, ideally it will be very small.

i'm leaning towards adapting an existing product like the headset idea, sorry i know this isn't strictly an arduino project.

I appreciate any recommendations.