If you get one that's rated for an iPad (2.5A +) then you can charge off the house bank (without deficit when the engine is running), and your alternator will replace any power being drawn. If you're going to add solar, I think it makes more sense to apply it for the house bank and charge everything from there.

Car chargers run about $10 - $30 with "branded" ones being more pricy. I have this and it works well.