We're currently using our Iphone @ the lower helm with the Garmin Helm app to stream & control charts, sounder ,radar ,etc from the Garmin 741XS on the bridge. That works great as long as the 741 is on. When we're just below, We have Garmin bluecharts/active captain downloaded to use as a stand alone unit (there's a small digital unit in the dash for depth). We're going to buy an I-pad off of e-bay because I do like the Bluetooth feature & the phone is rather small but I was under the impression that if I didn't get the cellular version with the embedded GPS that we could add an external GPS via the lightning port, such as Bad Elf, & it would work that way. Isn't this correct or am I mistaken?