Would be interesting if cells of groups of cells in a spreadsheet could show a subset of the UI of another graphical program on the system. If it could allow user interaction with that graphical program then even better. That could allow users to build a dashboard of their running graphical software. Has this been tried before?
Yes, on Windows this technology is called OLE (Object Linking and Embedding). It allows embedding (parts) of other applications' documents in a document. Nowadays only a few programs besides the MS Office suite provide OLE capability.
For example, you can embed a complete Word document inside an Excel cell by clicking: Insert -> Object -> Microsoft Word Document. By double clicking this object, the Word UI opens up inside Excel.
