Well I've tried it out just now and to my surprise it runs without any tampering with the phone. Just loaded the app from the store, created a folder for the BIOS and loaded up an image of the Japanese Disc 1 that I have lying around on a flash drive.
It does start up and it does run pretty fast and stable. About 70-80% of the time I got full speed.
The controlls do work but it's pretty clumsy to move Ryo with the virtual touchscreen controller.
What really nice is that you can easily use controllers with this emulator. The video already shows this with a bluetooth controller. I'm using a DualShock 3 that's hooked up through a USB OTG adaptor and it works great!
Besides the select button acting as the start button the controls are identical to a dreamcast controller.
Even the analog stick works perfectly.
One thing that's really annoying, the emulator doesn't tell the display to stay on while it's running and thus the screen will lock after the set time and turn the emulator off. At that point it shuts down completely and you have to reload the image file again. So if you have to lock your phone you'll lose all progress. They really have to address that issue quick!
In the end it's ultimately playable though and a damn impressive thing if you think about it.
The original Shenmue on a mobile phone!
But now comes the big problem... The emulator doesn't really seem to like the Adreno 320 that the i9505 S4 variant uses. It doesn't look nearly as good as in the video with the i9500. The graphics are... well look for yourself: