The original Eyefi Mobile app will work with both Eyefi Mobi and Eyefi X2 cards. However, it does not support any of the advanced Mobi Pro features — it only uses Eyefi's Direct Mode feature (that is, it directly transfers photos from a Mobi card to the mobile app).
We do not recommend that you use your Mobi cards with the older app. You will lose out on all the wonderful features we have implemented in newer Eyefi apps. We will not be making any changes to the older apps.
We hope the incredible offer we're providing is reason enough to switch to Mobi cards and Eyefi Cloud.