You could modify this example to activate the drive motors of a bot.
Consider setting your ESP to connect though local WiFi to internet. At that point you could setup an MQTT connection to a broker then do a web app to control the bot from anywhere. The ESP code is simpler, it's just handling an MQTT connection rather then being an AP and a web server.
http://mirobot.io
It's all open source:
https://github.com/mirobot