I had a staff magus that I took a dip of monk. I never got past 3rd level, but it looked like a cool character. I'm not sure about high level mechancis though.
Choose monk or magus, not both at this point.
Totally agree.
I'm of the opinion, that in general, a level (or two) in one of the utility monk archetypes (Maneuver Master, Master of Many Styles, Flowing Monk) can do a lot of characters some significant good, but further diluting your spellcasting is a bad idea.
Talk to your dm, see if he would allow flurry of blows to work with spell combat if you were only using a one handed weapon (maybe at the cost of a special feat). If you can get that then the monk and a kensai magus would synergize well. You wouldnt lose the bab, and you would get both int and wis to AC with whatever other armor bonuses you can get from spells and items.
Or change your order to be the one where you can make trip attempts against your challenge.
... as an immediate action, a flowing monk can attempt a reposition or trip combat maneuver against a creature that the flowing monk threatens and that attacks him.
This sounds like fun, but unless you're one of those people who rolls absurdly well, this is mostly going to waste your swift actions and/or suck up the majority of your feats. To do well tripping things, you have to put a lot of resources in. You'll need to take the maneuvers arcana for Magus and whatever the monk-equivalent is, or else you'll lose out by losing BAB in each class, in addition to taking the trip feats, which monk doesn't even give you a particularly good head start in. Also, you have to be fighting the right things -- there's TONS of monsters which are truly or virtually untrippable.
What level is your Samurai, and what are you trying to accomplish with Magus? Remember, neither monk nor samurai will advance your mount, who will become increasingly squishy. I'd say that up to 4 or so levels of Magus might synthesize nicely with a Samurai, since you'd lose only 1 BAB and you could take Boon Companion to bring your mount up to level. You'd pretty much be using Magus for the swift, stacking weapon enhancement. (Although the kensai's perfect strike ability to maximize damage would be pretty fun on a triple-damage-mounted-lance-charge, if you did decide to take monk levels and not wear armor.)
A level of monk isn't bad for Magus. A magus fights one handed so Crane Style would be useful. The level of Monk get you the prerequisite Unarmed Combat and Dodge feat. So you could take one level of monk and if that level gives you feat get crane style which give you the ability to fight defensively for -2 to and +3 to AC. From there is Crane Wing and Crane Riposte. Very nice for magus who has to fight one handed anyways. Add to that the +2 to all 3 saves, increased unarmed damage, and additional class skills and it's not too bad deal. But for me it would be the feats, much easier to grab a level of monk and jump into Crane Style in one level that way.
In agreement with most people here. You've already dipped into Samurai. I don't think another dip into Monk is going to be worth it. The only time I would ever mix Magus and Monk is with the Staff Magus and the Weapon Adept (two levels, maximum). You get a lot of fun, extra stuff that way to help out your quarterstaff.