The best replacement for altimeter is station pressure.

The best alternatives to altimeter are rated as following:
★★★★★  station pressure
★★★★★  barometer
★★  gps
★★  barometric altimeter
★  gps elevation
★  radio altimeter
★  sea level
  sea level pressure
  barometric
  sensitive altimeter
  gps altimeter

Your alternative for altimeter is not listed? Suggest!
Speaking about altimeter, one probably shouldn't forget about gps.

Other search terms related to altimeter and their ratings are:
★★★★★ gps
★★ barometer
★ pedometer
watch
You have in mind a companion for altimeter and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of altimeter in all years. Click on graph for more.
altimeter
station pressure
barometer