I bought the AFE Flight Timer.
ASA Flight Timer : ASA - Airplan Flight Equipment
It has all the features you might ever need in an aviation time piece. Six approach count up/down timers, a fuel timer, a stopwatch, local and UTC times, a 5-digit notepad, backlighting and it runs on a standard AA battery.
However, it's big. I've tried fitting it to my kneeboard, which didn't work. I've tried adding a lanyard and wearing it around my neck, which didn't work. It is way too big to fit around your wrist, never mind the fact that it doesn't come with a wrist strap. I haven't tried fitting it to the panel because I fly a multitude of club planes. I've simply run out of ideas where to put it.
So today it lives in my flightbag, mostly, and I just use my 10+ year old analog watch to tell me the time.
Your flight instructor was right. Keep it simple.