How about mounting the timer and any override switches in the house, maybe near the breaker panel. May not be an option if you don't want to walk to change it.
Offhand I don't know of any timer that can be remotely set. Doesn't say they don't exist, I just don't know about them. If you want to just do the on/off timer override that part is easy. For a couple hundred $$ yiou can do it from anywhere in the world.
Al