I have a GREAT android app on my daughter's smartphone. It is called PARENTAL TIME CONTROL. I select the times of day and days of week her phone is available for her to use. There are NO monthly fees! Here is the direct link:
https://play.google.com/store/apps/details?id=com.phone.lock&feature=search_result#?t=W251bGwsMSwyLDEsImNvbS5waG9uZS5sb2NrIl0.
No Nomophobia for her!
It makes me a better parent!