The best replacement for imessage is text.

The best alternatives to imessage are rated as following:
★★★★★  text
★★★  whatsapp
★★★  bbm
★★★  sms
★★★  text message
★★★  ichat
★★  mms
★★  kik
★★  hangouts
★  adium
★  sms message
★  viber
★  text message iphone
★  facebook messenger
★  bonjour
  message
  texting
  text message iphone5
  google hangouts
  bitesms
  text difference
  blackberry messenger

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

Other search terms related to imessage and their ratings are:
★★★★★ mac
★★★★ ichat
★★ google voice number
★ phone number on ipad
You have in mind a companion for imessage and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of imessage in all years. Click on graph for more.
imessage
text
whatsapp