I've been working on a ti-84 emulator for the nspire for a while now, and I think it's in a workable state now. It can boot up TI-OS, but it still has some bugs (the OS freezes if it's left idle for a while). It can save the state of the emulated calculator between launches.

Download
Source code

To use, launch it once to register the file association, then launch a rom file with the extension "8rom". The state of the emulator will be saved between launches in an "8sav" file. Launch the 8sav file to restore the state.

I know there was another nspire cx ti-84 emulator, but it often left the nspire unusable, and its author disappeared without leaving any source code, so it's not very useful.