A shared threat picture between the platform, the ground and other air defence fills the blind spot of the Sense layer. Military datalinks are the professional standard; for broader, low-cost use there is TAK/ATAK (Team Awareness Kit) — a free, widely used app for sharing a common operational picture.
Caveat
TAK/ATAK has no organic detection of its own: it only shares what other sensors feed into it. It is therefore a complement to, not a replacement for, the Sense layer in 7.1.
See the reference card TAK / ATAK.