You can now launch FCheck from within Maya by selecting File > View Image or File > View Sequence.
Maya uses FCheck as an image previewer to display intermediate results of a rendering. FCheck can be opened within Maya when using the following tools.
The Render > Show Batch Render function uses FCheck to preview the latest rendered image when batch rendering.
See Render > Show Batch Renderr in the Rendering guide on how to open FCheck when batch rendering.