Edit: model inputs available since Angular 17.2
Phase 2 (or maybe Phase 3) of Signals will introduce signal: true components, which will include two-way bindings.
The RFC https://github.com/angular/angular/discussions/49682 describes this under Model inputs.
In short (and API is subject to change) you will be able to define a special type of input that can be manipulated as a signal but will be a two way binding back to the parent.
But you won't be passing a signal directly, it will just appear as a signal inside the component.
If you're trying to pass signals to a component today you can do that via a service or just a normal input which is set to the evaluated signal value.