i agree with JohnSmith & benina . Mobile aplication cracking will be more popular in the future.

i think that nothing will change who reverse mobile apps hi will continue to do that who reverse programs hi will also continue with that

at least for me, my direction changed from dongle emulation tools programmer to .Net/android application keygener.
why?
1. nothing new in dongle world.
2. most of windows applications are now based on .Net and dongles are not so effective for .Net as for native applications.
3. there are a lot of useful android based applications.

chip reverse is tough job

Does exist some Android application protector/packer?

One of the best packer in android is Allatori

When I did search, Allatori was the only one that I found, but it's paid.

Does exist one that is free? (like UPX)

Now its +6year ;)
some words from 2014 is happen ...