If I write myself a note and put it somewhere, it acts as a constant low level reminder. I can walk past it numerous times and I can ignore it or act upon it. If I don't wish to act on it the next time I see it, it's presence is not enough to annoy me.
If I set a reminder on my mobile, I usually have to pick a specific time. If it's an appointment or something I have to do at that time, then that's fine, but if it's just a reminder to (for example) post a letter, I don't want to have to pick a particular time to do it, I want to do it when I'm ready. If I have to keep deferring (snoozing) a reminder, it quickly gets annoying because it's at too high a level for the type of reminder I want.
So what mobiles (etc) are not good at, is being able to set a background level for the reminder which is appropriate for the type of thing I want to be reminded of.
Back to my handwritten note
- I can place it more or less prominently
- I can use large or small text according to the urgency
- I can position it according to it's needs (on the door to remind me when I leave the house, or in my car if I need to get fuel before I drive somewhere far)
so - I have a massive range of flexibility - lots of different ways of making the note more relevant to certain situations
Because I am used to this flexibility, I feel my mobile is unable to provide the same level of flexibility, other than to remind me to do something at a particular time - assuming I have it with me and the battery is charged and the phone is on...
Now, if I could press a button on my phone that makes it beep/vibrate next time (or every time until canceled) I come within, say, 2 metres of my current location (or one of a set of previously defined locations), then apps along that sort of functionality might start to get seriously useful!