The Hudl2 is a real nice little tablet and best of all, it is affordable to keep a second as backup if one breaks. A friend put one permanently in his plane and is quite happy with it (he is an Android guy and loves to fumble around on the devices, but lack a wifey, so there may be some side effects ;-) ... but thats another story). He has a second device I have not seen in action, but maybe Rob can say a bit more wether that runs SD as well - it is this 20£ China tablet:
https://www.chinavasion.com/china/wh...t-Orion-Black/ (has no internal GPS).
If you are used to using awkward Garmin GPS "logic" menus, Android KitKat is not that bad, compared, but train on the ground before and enjoy i.e. SD. I was positively surprised how well it does its single job there, but as mentioned before, get a permanent power connection, or always take-off with fully charges battery, that is a weak point.