Hmm, interesting & I suppose it could be helpful. I also wonder what parameters you're working to, whether it will be an automatic app or it's a consult service?
We see all the time here that it is hard to take good hoof pics, and that if they're not taken squarely, it can give an inaccurate idea. So ensuring people take good, square pics is one hurdle.
The next is that you can't make accurate 'diagnoses & treatment plans' from photos, let alone from just one single angle. There are also different reasons for some 'signs'(there's more to it than just looking at a hoof) and some things look better or worse in photos than in real life. Some perceived 'faults' may also be correct for that horse/hoof, such as higher heels than 'ideal' and in some respects, 'ideal' is very open to opinion, as are specifics of treatment/trimming.
So... I'm imagining if it's an app, it will have to have a lot of 'disclaimers' & will only be good for very general, basic ideas. If it's a consulting service, you will need more than a few pictures to get enough to give more than that, and still, you can only give general type advice(albeit far better than nothing for those who have no 'real' support). I suggest you look at some of the 'hoof help' threads here & hoof pics that have been 'marked up' to, to see what's needed & what can be told from pics. I think we have a pretty nifty & free 'consulting service' here actually
- there are a few here who really know their stuff.
I can see this could be useful for horse owners, to recognise/consider what they're seeing, and for aspiring but uneducated & inexperienced farriers/trimmers.
Perhaps good for farriers who have a problem sharing their knowledge, to show their clients to help them understand. IMO a good farrier/trimmer should also be able to explain adequately without marked photos, and a good farrier/trimmer who feels confident enough to take money off people for the job most certainly shouldn't need instruction in what they're seeing... although in reality, many farriers & trimmers I know of would benefit from an app like that, to learn from surreptitiously...
So anyway, that's my opinion about what I imagine you're aiming for. Hope it helps.