I find similarities between certain ACT components and EMI (eye movement integration) technique (Steve Andreas, 1993; Danie Beaulieu, 2003), an alternative form of EMDR.
The client needs to be open to his difficult private events while doing the eye movement. Often, the eye movement produces a context to facilitate acceptance and it has the advantage of being a non-intrusive exposition to private content. Words that were so much affectively charged get defused during treatment and the client does not react to them anymore. I find this intriguing when comparing it to RFT and ACT.