Apogee Jam, goes via usb to lightning, and takes guitar 6mm plug input. Mine has a manual gain adjustment on the side. Small, tidy. Works in iphone and ipad. Ipad accepts it as below 100ma without complaint.
I ended up miniaturising all my gear now i focus on GB in an ipad.
ASIDE…
On Usb to lightning, Apple is tightening up on the unathorised kit all the time - proper ones have an authorisation chip supplied by apple, built into the lightning end. I have a dozen non-approved (non-MFi ones) that used to work fine, and they cost me about £100 all-told ie not cheaper in long run. Dead cables in effect now. Iphones are less stringent, but Apple will change that I feel certain, or let obsolescence be the arbiter in due course.