Casio scientific calculators do have an internal representation of π (it's treated differently from the closest possible typed value) and very nuanced representations of numbers in general.
As you say, this is where calculator apps almost inevitably fail - representing numbers properly is really crucial to the UX, and floating point numbers are not sufficient.
Casios are a mess. They are actually made my Kinpo which do a shitty job of pretty much everything. The notable exceptions being the FX991MS and Fx5800P which are very very close to my 50g (which was laboriously tested on paper before I trusted it)
50g is basically a 48GX emulator with 400MHz ARM core that emulates Saturn, MetaKernel and a CAS. Goes like lightning. Oh and a bigger screen so you get 7-9 stack lines. Also you can use SD cards as ports. Mine has 256Mb of Flash. Eats a set of batteries once a month but it's worth it for the power.
I can create a symbolic list with 50,000 entries in quite happily on the device then do all standard two-variable stats on it in 1-2 seconds.