Six people writing at once
The demo above is yours alone. The real one is a party of four to six plus a game master, all editing the same sheets in the same evening, which is a different problem and the reason this waits for a database rather than a clever component.
Every change has an author
Damage, healing, conditions, rests and spent resources are events with a name and a time on them, never an overwritten number. Current state is a fold over that log, which is why undo can be free and why a wrong number is one tap to fix instead of an argument.
The game master's dashboard
All four to six sheets on one screen, exactly as above, with damage and conditions applicable to anyone at the table. No asking six people to read their hit points out, and no player waiting to be told what they already know.
The notebook, shared
The one below works and is yours alone. The real one is the same notebook with five other people writing into it as the night happens, kept between sessions, and searchable across every session you have ever played.
It picks up where you left off
Hit points, slots and conditions are still where they were at the end of last session, because nobody remembers by Thursday. The session before is on the sheet rather than in somebody's memory.
Any character, from either builder
An SRD character and a hand typed custom one resolve to the same sheet, so the tracker cannot tell them apart and never asks what class anybody is. Bring homebrew and it behaves exactly like everything else here.