Designing custom magic items is kind of a fuzzy art. Expect to tweak things as necessary. For adding spell like abilities like that, I probably wouldn't work them in like enhancement bonuses. I'd probably consider it a separate ability according to the magic item creation guidelines.
Command word activated is the usual method and the guidelines are priced such that you don't need UMD to activate it unless it has a restriction on race/class/alignment/whatever that you don't meet.
The only real limit on doing it this way is money and GM approval. To cast Fly 1/day with a command word for five minutes at a time, it'd cost 5,400g market price, if you go by the guidelines.
Now when you have multiple abilities in a single magic item, the most expensive ability costs normal price and every ability after that is priced at 150%. I'm not sure how this ought to work in relation to actual armor properties (either enhancement equivalent or flat rate abilities). The simplest way is probably to just price the proper armor abilities as normal and add in special stuff at 150% regardless of what it costs. So in that case, you'd price in 1/day Fly at 8,100g.
Using those guidelines, Detect Magic and Open/Close 1/day on magic armor would run 270g each. Permanent Feather Fall clocks in at 12,000g and a continuous Fly rings up at a big 90,000g.
Keep in mind, inventing new magic items or applying enchantments that aren't laid out in the book is kind of rough and the directions for doing so are guidelines, not rules. You're already in houserule territory by making custom stuff, so if you think it'll work better as enhancement equivalent, go ahead and do so.
