Thank you so much for taking on this challenge idea.
I like your design and the first design iteration looks promising.
1) Probably want to use a spring or some mechanism to return the lever back when released. The spring tension should not be very default to double press however.
2) It would be great if the holding component can be replaced for different phone thicknesses and phone cases.
3) You may want to add some indent to surface touching the back of phone. This may not be necessary and can probably tell if it’s needed after first print.
I appreciate taking time to work on this challenge and looking forward to see the next iteration of your design.
Collaborate with makers in the community to develop your device idea.