There is not presently a way to inspect the remaining per-frame quota (or other limits) from within executing scripts.
As a developer you can get a rough idea of how close your scripts are to quota by enabling the "Script Profiler" feature from within the Decker menu. This will display a live chart of the percentage of quota scripts have consumed over the past few seconds.
If you want to provide the user with visual feedback during long-running scripts, you need only draw visible updates from time to time. When a script runs out of quota it is simply paused momentarily to allow Decker to service input and then automatically resumed, unless the user explicitly halts it.