It's a friendly advice: Please do not put many efforts on this project (unless you have some extraordinary plans for it)

Anyone can send himself WhatsApp msg without any website/app.

You should try: - Save your WhatsApp number in the phonebook App - Open phonebook app and look for your number - Choose "Message +X-XXXXXXXXXX" option (with Whatsapp icon) - It will create a new chat in your WhatsApp

Another way: - Just create group with one contact and remove it later. Now you're all alone in the group and can use it as Notes app.

Good luck for your venture.