Richard, what Frank's talking about is using the cellphone as a really really smart shutter release/camera controller, not as the main image taking device.
I haven't used Helicon focus. And if I were going to try doing something like that, I'd probably use MagicLantern instead, because my 5DmKII and 50D both have builds that allow for doing
stepped focus racking. But I'm still too busy trying to suss out the Auto-ETTR and dual-ISO modes in ML to try it.
If you're geeky enough that firmware add-ons hold no fears for you, and runnning scripts hold no mysteries, you might be able to achieve something similar
with your SX50 and the CHDK.