If you're a bullet journaller, this is the kit you've been looking for! The Pebble Stamp Kit.
It's a set of 39 stamps that are perfect for stamping dates, calendars, days etc. They align to a 5 mm grid (so work brilliantly with the Pebble Traveler's Notebook, though any 5 mm grid is compatible, obviously!).
For those of you unused to the world of stamps, these clear stamps adhere to acrylic blocks (very cheap to buy online). They stick soundly enough to use; the clear acrylic block and clear stamp means you can see exactly where you're stamping; the stamp (and block) are easy to wash; when you've finished with the stamp, you just peel it off the acrylic block and stick it back on the plastic sheet it came on. All of the 'sticking' is through electrostatic forces - no glue is required.
There are the days of the week as M T W T F S S (i.e. a Monday start), plus a S M T W T F S (i.e. a Sunday start), that will line up across 7 squares. These could be used with the 7 perpetual calendars, where the first of the month starts on a different day, to give a snapshot of the month - perhaps if you just want to circle days. Where a month doesn't have 31 days, it's easy to swab the ink off the extra numbers with a cotton-bud or similar (or use correction tape after you've stamped!).
I would use them for daily trackers - stamp the days across the top and indicate what I was tracking down the side. If you wanted, you could combine that with the five squares, so you had something to tick. The squares obviously work as 'to do' tick boxes as well.
The days of the week, months, and numbers allow for weekly and monthly spreads to be created easily, and also to label individual days in a daily spread. I use a blank notebook for a daily diary, and would use these to stamp in the month, day and date across the top of the page.
You can see how the combinations have been really well thought out. In the Pebble TN, there are more than enough pages to have monthly spreads, plus weekly spreads, and still have pages left over for collections or notes. I've never quite managed to cope with a bullet journal (because I have so much forward planning, so need to set out the whole thing like a diary, somewhat defeating the purpose!), but this combination may just convert me!
Pebble Traveler's Notebook (200 pages of Tomoe River paper!)