Gee - sorry if I tried to cover all the bases. The OP didn't specify what model of iPhone he had and not only does that affect things - so does the OS he's running as every app has minimum requirements and some I can't even run on my relatively recent but now discontinued iPhone 4.

Regardless - if I was going on a 30 day bicycle trip and thought I needed GPS - I'd buy a dedicated GPS unit. An iPhone has a digital camera built in too but a dedicated digital camera still does a much better job.