thing1.py

#!/usr/bin/python

import subprocess
import time

RUNNING = 1
STOPPED = 0

global state
state = STOPPED

def foo():
    global state
    global proc
    if state == RUNNING:
        print"Stopping thing2"
        proc.kill()
        state = STOPPED
    else:
        print"Starting thing2"
        proc = subprocess.Popen(["python", "thing2.py"])
        state = RUNNING

while True:
    raw_input("Press Enter:")
    print ""
    foo()
    time.sleep(1)

thing2.py

#!/usr/bin/python

from time import sleep

while 1:
    print "I'm alive"
    sleep(1)