The best replacement for keyboards is piano.

The best alternatives to keyboards are rated as following:
★★★★★  piano
★★★  yamaha
★★★  digital piano
★★★  pianos
★★  casio keyboards
★★  membrane
★★  yamaha keyboards
★  synthesizers
★  roland keyboards
★  synthesizer
★  rf keyboards
★  workstations
★  casio
  digital pianos
  voice recognition
  regular keyboards
  korg

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

Other search terms related to keyboards and their ratings are:
★★★★★ keypads
You have in mind a companion for keyboards and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of keyboards in all years. Click on graph for more.
keyboards
piano
yamaha