I'm also an avid cyclist using Garmin Ant+ heartbelt direct to my trusty old wornout Xperia S and also Xperia Ion too.
Many say BT4.0 LE still has cutoff issues, and Ant+ batt last forever in heartbelt.....
I understand from speaking to shops that the LTE version has Ant+, but many said the 3G version does not. The SnapDragon 800 does have Ant+ feature in chip, there was some debate if 3G version uses this chip. Sony really should fully enable these by firmware if possible.
PS: The bluetooth signal needs to be switched on to enable Ant+.
Hope any of you could provide your experience of workability or lack off, thanks.