iStat Menus

CPU, GPU, memory, disks, network, sensors, battery and weather, all as menu bar items with history graphs.

What it does

iStat Menus puts live readings in the menu bar and detailed history behind each one: per-core CPU, GPU activity, memory pressure and compression, per-disk throughput and SMART status, network throughput with per-process breakdown, every temperature and fan sensor the machine exposes, and battery health with cycle count.

The dropdowns are the real product — clicking the CPU item shows top processes, so “why is this fan on” takes one click rather than opening Activity Monitor.

Notes

Paid, with a free trial. A licence covers major versions, not upgrades between them.
Sensor access needs a helper tool installed with admin rights.
Overlaps heavily with btop, Mx Power Gadget and macmon; the difference is that this one is always visible without opening a terminal.

Alternative to

Alternative	Type	Trade-off
Stats	Open source	Covers most of the same menu bar readouts
iStatistica or Sensei	Paid	A dashboard-first design
MenuMeters	Free	Minimal, long-standing
Activity Monitor	Built in	Enough to answer most questions