Currently SQL Monitor does not have a way to identify and alert on heap fragmentation. I suggest you add this to the product.

I know having a heap is usually a bad idea and that heap maintenance is a pain (rebuilding a heap also rebuilds all the nonclustered indexes on it, SQL Server doesn't release a page of a heap table, and doesn't use free space in previously used pages unless you are doing deletes with TABLOCK hints), but there are some valid use cases for heaps.