Any of the Helix 9 series, Helix 10 series, and Helix 12 series will share data with your 1199ci HD SI Combo via Ethernet.
The Helix 12 CHIRP SI GPS is the replacement for the discontinued 1199ci HD SI Combo. Same MSRP with a 2" larger display that is much brighter and has CHIRP 2D sonar. Uses the same transducer as the 1199.
You can also cross-share sonar technologies such as using a Helix Sonar GPS unit to display Side Imaging and Down Imaging from your 1199. Same with a Helix DI GPS model.
Both units would need a AS EC QDE Ethernet adapter to connect the Ethernet cable to them.
You would not be able to share map data, each unit would need its own map card. Humminbird units read Navionics and Lakemaster digital mapping.
Humminbird Helix 12 SI, 1198c SI, 1198c SI, ONIX 10 SI NT, 360, RC-1