This python script will reboot your DigitalOcean droplet if the hostname is unreachable or returns a status 500 or 503. All you have to do is edit the variables. Can be scheduled as a cron job.

checkVPSandReboot.py

#!/usr/bin/python
import httplib
import subprocess

############################## Site To Check #################################
VAR_hostname = "yoursite.com"
VAR_path = "/"
######################### DigitalOcean Variables #############################
VAR_dropletID = "123456"
VAR_Token = "YOUR_API_TOKEN_HERE"
##############################################################################

def get_status_code(host=VAR_hostname, path=VAR_path):
    try:
        conn = httplib.HTTPConnection(host,timeout=1)
        conn.request("HEAD", path)
        return conn.getresponse().status
    except StandardError:
        return "Err"

checkStatus = get_status_code()

if (checkStatus == "Err" or checkStatus == 500 or checkStatus == 503):
	shellCMD = "curl -X POST \"https://api.digitalocean.com/v2/droplets/" + str(VAR_dropletID) + "/actions\" -d'{\"type\":\"reboot\"}' -H \"Authorization: Bearer " + str(VAR_Token) + "\" -H \"Content-Type: application/json\""
	p = subprocess.Popen(shellCMD, shell=True, stdout=False, stderr=False)
	retval = p.wait()