Two rough concepts: One about biofeedback, the other thinking more about 4D printing and flowers.
There have been many projects that connect heartrates or other biometric readings to wearable “tangible” output or other people. See
http://www.thetouchx.com/index.html#Home
The idea of discretizing interactions with 4D printed devices by freezing cubes of reactants/solvents is interesting. Keep developing.
P.S. I did the code to print the Harvard flowers – can help with 4D printing.
-Dan
Udayan’s comment: Enough work has been done in the past on connecting heartrate to a physical output and so on. But, you could build up on other interaction scenarios and it could be interesting. Take a look a this inflatable jacket and this helmet. Maybe you can build on top of these existing objects by defining more concrete scenarios within the space of transformable objects.
The morphing over time idea is a good direction, but why ice cubes? This direction similar to the previous one needs more concrete scenario.