I too use Beetight and would recommend it. Nevertheless it has its shortcomings, of which the inability to handle data off line is, I would agree, the greatest. If there is change of wind direction, or the neighbour's cat sneezes, or whatever, I lose mobile coverage. Apart from the possibility getting propolis on the 'phone, entering data with a gloved finger is an issue, simply solved by keeping a cheapo touchscreen stylus pen in my beesuit.
So I would suggest looking at the functionality and interface of Beetight, and thinking about how they could be improved
Thanks for the suggestion, I will look at the app