Calculators that allow direct operations on data stored on persistent storage?

[mfleming]

If you mean calculators with internal or plug-in memory that can be treated like a file system, then the HP-41 with expanded memory (XM) or a HEPAX memory module can do the trick. Diego's NoV-64 provides four 4K pages of HEPAX RAM that can be bank switched with two other sets of four pages, all in persistent ferroelectric RAM. The 41CL has 128 pages of static RAM that can be plugged in and formatted as HEPAX RAM.

~Mark