The Web Contact Picker API is now available in Chrome 80 on Android M or later, providing developers with access to users' contacts while maintaining security and privacy expectations. The API consists of the ContactsManager object, which can be accessed through the navigator object. Developers can check for support by verifying if the "contacts" property exists in the navigator object and if the "ContactsManager" property exists in the window object. Once supported, developers can use the `navigator.contacts.select` function to show a modal interface that allows users to select contacts, which returns an array of contacts with requested properties. The API requires a user gesture and will only run on secure domains, and it does not provide permanent access to users' contacts. To add this feature to an application, developers need to check for support, trigger the API when a button is clicked, listen to the click event, call the Contact Picker API, handle the response, and fill in the input with the contact's number.