I prefer as few contexts as possible. Here is how I would handle something like this. I would first put the reminder on my @Errands list. During my weekly review I would notice that this particular task isn't getting done and is not likely to get done unless I make a deliberate effort to take the watch to the shop. I would then plan a trip to the watch store and put it on my calendar as an appointment. I would also set up timed reminders to put the watch in my pocket or briefcase before I left for work (assuming I wanted to do the errand on my lunch break). The best solution, of course, is whatever works best for you.