I had similar experience with what you are trying to achieve.

There's a built-in function called "Planned Activity" in Odoo.  I recommend you to look into that before implementing your own module.

In your model, you can call any records from any table based on your desired criteria.

For reference, 
# -*- coding: utf-8 -*-

from odoo import models, fields, api, _

import logging

class Todo(models.Model):

    _name = 'task.management'

    _description = 'Task Management'

    _inherit = ['mail.thread', 'mail.activity.mixin', 'portal.mixin'] 

# display this one2many in a form view in .xml files

# One2many must have another many2one in the related model, 
# In this case it's 'task_summary_id' I made in 'mail.activity'

my_tasks = fields.One2many('mail.activity', 'task_summary_id', string='To Do', domain=[('activity_type_id', '=', 4)]) 


​

The above is an example.