See Who is Connected to Your WIFI Through Your SmartPhone 2017
There is an App Called Fing Shows You All the Devices Connected to Your Network
Android/iOS: Fing shows you all of the devices on your network, down to the device type and manufacturer for each. Best of all, it puts all of that data in the palm of your hand.
Fing has been around for a while, but it's a quick solution for anyone who wants to take a peek at network activity from their mobile device. Just launch the app to see a list of connected devices, their IP and MAC addresses, customisable device names, and manufacturers. Tap a device to add notes, as or change the name, icon, or location. In addition, Fing keeps a full history of your discovered networks for reference.
Fing is a handy app for day to day use of knowing who you're connected with.
It's available for free for iOS and Android.
Fing - Network Tools | Google Play Store
Fing - Network Scanner | iTunes App Store