This tutorial is a guide on how to modify the HUD (also includes the overworld border, stripe image, and even sprite OAM and pixi sprites). It also includes various custom subroutines and sample codes on how to use them.
A patch DefaultTiles.asm that modifies the status bar and hardcoded tiles in a user-friendly way, unlike Smallhacker's status bar editor
32-bit HexDec (ideal for big currency system)
RepeatedSymbols (display how many n items out of x)
left/right-aligned number display (suppresses leading zeroes instead of replacing them with leading spaces)
Leading zeroes remover (replace them with leading spaces)
32-bit frame counter to timer display (ideal for timer manipulation; i.e add 5 seconds without dealing with individual units if a unit overflow occurs)
Several sprite and stripe routines to write the info.