How can I build raspberry pi that will encrypt calls on my phone (say lets VoIP calls, as cellular ones are harder but still an option). The rasp Pi would need to be connected in-between my earphones and my iPhone. There seems to be a product that tried to do this and launched on kickstart but they seem defunct now (https://www.kickstarter.com/projects/620001568/jackpair-safeguard-your-phone-conversation). I cant seem to figure it out whether theyre defunct because of lack of demand or due to product not working well.