Similar to how you can two-way bind [(ngModel)] you can two-way bind custom property on a component, for example [(value)]. To do it use appropriate Input/Output naming:

@Component({
  selector: 'super-input', 
  template: `...`,
})
export class AppComponent {
  @Input() value: string;
  @Output() valueChange = new EventEmitter<string>();
}

Then you can use it as:

<super-input [(value)]="value"></super-input>