Smart thermostats are very popular. Nest and Ecobee are the most popular brands. The Ecobee has remote occupancy sensors, which is important if you have a multi-level home. The thermostat is easy to install, if you have modern wiring - otherwise it can get complicated. Mostly because you'll need to connect power from the furnace to the thermostat, which requires connecting an extra wire.
The thermostat can turn on the heat it's too cold and turn the air conditioner on when it's too hot. You can also control a humidifier and run the fan for 5-30 minutes per hour, even if heating or cooling is not needed. The humidifier control is the biggest benefit I got from it. It monitors the humidity level and keeps it consistent.
The thermostat is connected to your WiFi router and can store data on the Ecobee website. You can monitor all sorts of things using your login. The smartphone apps provide the same features and you can control the unit from your phone the same way you do on the unit itself. The user interface is identical. It also looks really cool on the wall.
My electric company AND gas company offered rebates which added up to about $100 and it was very easy to file. Well worth the investment.
Amazon a service to install it for $70. I recommend doing this even if you are pretty technical - my installer found the humidifier wasn't working at all and fixed it - so it's a good way to get a little tune up for your heating/cooling system.