I don't do Iphones.
It is my understanding that you can not import routes in iPhone Sygic. @ScubaCinci tried and failed, and he is no slouch on tech. Lets see what he has to say about that to be sure
You can modify the route manually on Sygic.... you can drag and drop the route but on that small screen it really sucks and is only usefull for minor route fixes.
One option is get a cheap used android phone. You dont need to put it on verizon or whoever you can do it all via wifi. Bit then you have to learn android...get a google account and carry two pbones.
Might as well by a Garmin man.