Let's say I have to buy some superconducting magnets in my local store, but it's not particularly urgent; I'll just buy them whenever I'm near that store.
Let's say I have to go through some safety interlocks at various locations every now and then and in order to do so I have a particular retinal-scanning procedure to go through each time.
How could I store to-do items like this? They are not based on time, so are not suited to a calendar, and they are not simple items on a list to do at any-old-time. They are event-based: I buy the magnets when I'm at the store; I get the retinal scan when I'm going through interlocks.
What kind of program (open source) do I want for this? I would want the to-do item "buy superconducting magnets" to appear when I'm near the store (maybe I tell it; maybe it figures that out) and I would want the retinal scan procedure to appear whenever I'm going through an interlock.