This may not be part of PiHole's remit as it is obviously an ad blocker but it it does show a a lot of network activity. Suggestion so what would be very useful is an indication when a 'new' client joins the network.
Appreciate the network list can be viewed but the host names can sometimes be a wee bit confusing.
Geoff
You can do that (if and only) when Pi-hole acts as your DHCP server.
I have it implemented and it looks like this:
It is done at pihole-FTL(dnsmasq) level with an additional configuration file.
Integration and conditioning + message delivery would have to be coded separately and formed around the notification provider.
I use Pushover but it can be implemented with anything that sends stuff...
Emails, push notifications, smoke signals (not this one).
Check out -6 --dhcp-script= here.
That looks interesting, thanks for the link.
Geoff
If you use a unif controller there are a option to get mail when a new user join your network 
