Do you have enough of iOS on your iPhone 6/6s/6 plus/6s plus? That's great couse we have Mesuit - etui with battery (1700mAh for smaller models and 2500mAh for bigger), internal storage (32, 64 or 128GB) SIM slot and... Mesuit 1.0 which base is Android.
Android based Mesuit runs through lightning and app what makes it unique solution at the moment.
Prices are quite resonable: $150 for smaller and $165 for bigger. Prices are probably for 32GB versions.
Source: telepolis (polish)