I've set up a tablet or old decomm'd smartphone before on my home network, with BMS monitoring or any desired app installed on it (device rooted, in my case), so I could install VNC Server on it (gives terminal server, like Remote Desktop feature), then using Dyn-DNS (if you have a dynamic DHCP public IP) in combo with Open VPN server on my home router, so I can connect using Open VPN client into my home network gateway from anywhere, then I can use VNC client from either my smartphone, or VNC client from a remote laptop (using Open VPN Client connection), I can remote into the tablet or smartphone and control it like I was there... My home router is a Linksys WRT1200AC, and it supports Dyn-DNS account, and Open VPN Server...
NOTE: If your ISP doesn't offer public IPs, then in many cases you can have them set up a static NAT/port forward to route a port from their Internet Public IP to your private WAN IP to allow connection to your listening Open VPN port. But I've found that most ISPs offer public WAN IPs now. If they will give you a static public IP, then you don't need Dyn-DNS, only need that if your public WAN IP changes (is on DHCP), then Dyn-DNS allows it to auto-update the IP when it changes, so you can just access your VPN using a Dyn-DNS assigned hostname...