Found this emulator few weeks ago and I can tell you that it is a best emulator of ATARI I've ever used before.
Small introduction:

CastCE is a fully functional Atari ST emulator for the Pocket PC with support for literally hundreds of great games. CastCE Features:
- Very compatible - runs loads and loads of games and utilities!
- Runs many games at 100% speed on a 206mhz IPAQ
- Very good PSG sound emulation
- Not quite so good ST-sample emulation
- Low res & Medium Res graphics mode
- Emulates raster effects correctly
- Can read .st .msa disk images, supports zipped disk images
- Mouse emulation using the stylus
- Joystick emulation using the keypad or on screen joystick or anywhere on screen
- Keyboard emulation using the on screen keyboard
- Save state function to store your half finished games
- Programmable hardware buttons
- Supports different TOS ROM versions: 1.00, 1.02, 1.04, KaosTOS
- Autofire option
- Visible SpeedBar
- Patch-Function
- Button to change disk Quickly Install instructions:
- Just unzip the directory on your PC or MAC.
- Get a TOS rom (1.0,1.2 or 1.4) then copy it in TOS subdirectory.
- Copy all your disks image in DISKS subdirectory.
- Copy entire Directory using Activesync anywhere on your Pocket PC.
- Start CastCE1.2.exe on your PocketPC and choose yor TOS rom.
- You can go to GEM dektop by just pressing RESET or load a game.[/quote]
I love it. Just wanted to find author's website but cant find it

EDIT:
Oh my god I just noticed, do you know who is a developer of this program?!
SCHTRUCK!!!

hehe nice, ill check it out

Wow Schtruck even made an ATARI emulator? He sure is great! =)

ha yes, i did that somes years ago with a Cool english Man! Andrew Gower!

Our first version were coded in just 3 month!! it was incredible!


I don't know if it work on last end device, but adapting it has already been requested on last christmas.... i should take a look on it...

and the site is here:

http://perso.numericable.fr/schtruck/castce


while old domain http://www.pocketinfinity.com was lent by Andrew Gower, he closed it 3 years ago... and i never searched to buy it.

The keyboard kinda looks like the one of Qemu

I'm gonna try it on my HD2

I believe it's time to bump this thread.
CastCE was my favourite emulator long time ago in the good old Pocket PC times.

An Atari ST emulator is one of these things, that never released on Android.

Are there any future plans to port CastCE for Android as a second project besides FPSE ?

Yes, that would be nice