How tight were you with the guy?
I did a similar thing last season. Offered a guy a scholarship, he really wanted to come play for me. Told him I was redshirting him - he was OK with that. I then pulled the offer because I thought I had better chances elsewhere. Anyways, I ended up offering him the scholarship a second time, and he signed. No problems, no complaining, he didn't even say anything when I pulled the offer.
If you're in a battle with another school, though... I don't know. I would make contingency plans just in case. Hope everything works out for you whether you sign him or not.
Also, recruiting from phones can be really annoying (First World, 2015 problems). I hope this app seble is working on actually does make playing HD on a mobile device easier.