I do have a Canada Topographic Maps app on my iPhone which displays downloaded maps (quadrants that are stitched together).  I currently have Quetico maps loaded, but I've also downloaded WCPP maps and a couple of other locations.  It does have a couple of features on it to (for example) mark a route and establish distance.  I have also downloaded overlays from other applications that have things like campsite locations.

But if you are asking me, do I carry this in the field ... the answer is NO.  If you desire to do so, I can also tell you that the app will work in a totally "off line" mode.  So you need no reception to use it, but it also is not pin-pointing your location like a GPS.  In addition, the connectivity component can be turned on and off via Settings on your iPhone (all apps requiring connectivity are listed under Privacy/Location Services), which will pin-point your locations.

As a general rule, I have most of the apps requiring connectivity turned off because they persistently "ping" to establish location, which results in a significant battery drain on your phone.  If you don't want to charge your phone on a daily basis, this is one means to achieve that.

dd