I currently use a cycling app on my phone to track outings and it does well enough, but it takes a toll on the phone's battery. I was thinking since I want the depth-finder anyway I could get one that does tracking and have a better (larger, anyway) screen while saving the phone battery for more critical uses.
The program I use now (CycleMeter) will give me about 6-7 hours of tracking - if I keep the screen off. If I leave it on the battery is dead in just 1-2 hours. Connecting a charging cable is problematic since I keep the phone (iphone 5s) in a dry bag.
I also figured something with real buttons might be easier to use than trying to pinch-zoom and pan around on the phone through the dry bag. I tend to get frustrated with the phone when I'm trying to locate something on a map while using it my car, on the water with the phone in the dry bag it's 10x worse!
I took an initial look at the Lowrance units a couple months ago and was thinking about the models in the $500-600 range, but I'm willing to go higher if it's really worthwhile. The TI and associated gear is a large purchase and I want it done right, would rather spend more and get what I really want up front. The money is already set aside so what the heck!
As for exporting, looks like GPSBabel will do what I want and works on OSX or Linux. It appears I just copy the files straight off the SD card for Humminbird or Lowrance so should be easy. The two-SD-slot point is a good one, I'll have to consider that although currently all the two-slot models appear to be the very latest $1k+ versions.
I stumbled across Humminbird's "360 degree sonar" option while browsing their site. Drool!
Very cool looking, but just a wee bit overkill for my needs - and the price...!