After I posted this, I started thinking about it. I was the victim of a home invasion last December. My IR on my RPi camera wasn't working properly, so I only got poor quality pictures and the four men were not identifiable. I have since soldered the connection and fixed it. But, if the RPi stopped recording because it could ping my phone, it would not have recorded anything at all. So, it is a potential feature that I would need to consider whether or not I would use. I would imagine it would need to be tied into a better schedule. For example, if it is from 6:00 AM and 10:00 PM and my phone is in the house, don't record. If it is in the middle of the night and my phone is in the house, record.
It is pretty simple to configure your router to always assign the same IP address to your phone's wifi. I would think that anyone that can setp MoteionEye can figure it out. =0)
Also, even if you don't give it a fixed IP address, you can usually find the name of your device and maybe it could be pinged instead of by IP address. Just some thoughts.
Love your work,
Jimmy