I wanted this function as well and I just downloaded "BBClendar Free" and it works perfectly for this, better than an inexpensive digital watch!
Just go to the Advanced section, enable the hourly beep and even set which hours (mine is 8 AM - 10 PM) and what minute of each hour it beeps on. Just be sure to leave the program open when you go on standby or it won't beep.
As the App's description says, "Hourly Beep helps you to take a moment to rest in a busy day for every hour."
Enjoy!