You can use the Mobi app for shops that are on Shopmetrics, and it works great. For the shops that are on Sassie, you can try to use Sassie on your mobile browser. It will work, and it is better than doing it later, IMO. However, it will be slow and a PITA. And not the tasty sandwich type of PITA.
The jury is out on Sassie gas brands. Some of us prefer the PITA situation of using sassie on site. Others prefer the PITA of waiting until going home to upload photos and finish shops. Both a PITA. I prefer the former.