This app was mentioned in 12 comments, with an average of 1.33 upvotes
Consider MyLifeOrganized I use it in combination with the desktop client. Not sure how much ia restricted to the Pro Version vs the free version but it has almost all the features you requested but Pebble integration.
The interface is a bit old and clunky, bit a brand new version 2 with a clean modern interface is in beta testing at the moment (but no official Eta yet).
The desktop client is what I use most and is one of the most powerful clients out there. Unfortunately there is no Web version though.
You might try My Life Organized. It's very powerful but can be very frustrating to set up. It does have both Android and Windows apps
https://play.google.com/store/apps/details?id=net.mylifeorganized.mlo
This is way more power than you what you describe but MyLifeOrganized has a superb notification shade widget, one of the actions of which is to create a reminder five minutes in the future. I use it the way you describe and then use the full app to organize the todos I can't get to right
If you want a quick and simple task/life manager, I highly recommend "MyLifeOrganized" It's a freemium app on iPhone, Android and computers.
I like this task manager because you create subtasks for anything you need to do with the click of a button. In your case your task folders will probably be "Classwork, Work schedule, upcoming events" Then you could put subtasks under those main ones (and those subtasks can be divided into further subtasks if you need to). Then it automatically prioritizes your tasks into order of importance and puts them in your calendar (calendar is premium only) for you.
The android version lets you use it's premium version for free for 40 days, after that you need to pay $30 for the full version. It has all the features above but it also adds the calendar to the app so it's easier to sort tasks. The app's calendar can sync up with your phone/gmail calendar.
The learning curve is like learning an android: it takes about a day or less to get used to, but you'll find that it has so many more features that make it simple and easy to use.
I could go on and on, but it's probably best if you just check it out yourself. https://play.google.com/store/apps/details?id=net.mylifeorganized.mlo&hl=en
Personally, I don't have the the premium version but I've done the 40 day trial for it and I can say I don't really use the calendar and won't pay the $30 for it at the moment, but I will say that the options you have in the free version are well worth downloading the app. If you do decide to use the app, just use this for a quick tutorial. https://www.youtube.com/watch?v=NYEeEQ94UG4
So did I, until I found MyLifeOrganized. Seriously, it's amazing. Go look it up. It's available on Android, iOS, and Windows. It may take a while to get used to, but the important thing is put absolutely everything you every need to do in it.
This looks promising, multi-level in app image. https://play.google.com/store/apps/details?id=net.mylifeorganized.mlo
My life organized https://play.google.com/store/apps/details?id=net.mylifeorganized.mlo