Hi,
I'm new to Salesforce & I'm having a business requirement where I need to create a new app in Salesforce AppExchange. I wish to create an app where I need to provide the functionality of calling to the leads/contacts present in Salesforce. The design for my app would be as follows:
An app will be provided in Salesforce app exchange, on installing the app into my account a button will appear in Salesforce ListView named 'Click To Call'. Once the user clicks on this button then calling will trigger on the selected contacts one by one. At the click of this button, a calling pop-up will appear on screen(due to the app installed in the Salesforce account). Once the pop-up arrives before the user, he interacts with the person who has been called and disposes the contacts after selecting appropriate fields from the call pop-up. On call dispose, an API will hit my server for syncing the data relative to calling on that contact. 
I have already developed all the APIs for calling & syncing on my server, now I need an app to do the same from Salesforce side.

Thus for building this app I'm in need of writing some server side code which could hit the API's of 'phone calling functionality' which are already present on my server. Also, I need to write the HTML & Jquery code for designing the call pop-up within my app.

Can you please suggest me the resources which I shall consider for building such an app & host it on app exchange or just guide me how on Salesforce side can I begin with its development.