list_updated

No, there is no special helper for input updates, but you can still react to input field changes if you use $submit_on_change parameter in e.g. text_row() helper. For example, if you have text input named 'sample', you have to observe $_POST['_sample_changed'] in page request, which is send after the input field value change.
Janusz

No. Look into includes/ui_inputs.inc file. HEre you will find submit_on_change parameter in some ui helpers - those are optionally activated on content change. But this should not be big problem for you to implement such field, if you need it  in your code .
Janusz