The traditional "clansman's badge", ie: the buckle and strap with motto around the crest of the chief is 100% okay for a tattoo as it serves the same purpose as a "clansman's badge" pinned to the side of a bonnet-- allegiance to your chief as the head of your clan. Any other heraldic tattoo brands you as the property of the owner of that heraldic devise, or as someone displaying "bogus" heraldry.

The rule that is applied here is that of blazon. If it can be blazoned (that is, described in precise heraldic terms) then it is heraldry. If it can't be blazoned, then it isn't heraldry.

So, what is the status of putting the crest on a heart and then setting an "Irish" crown on the heart? Lets see... the "heart" becomes a sheild and the "crest" becomes a charge,while the "crown" takes the place of a crest:

Blazon: Gules (red) a heart thereon a tower argent (white, silver, or grey) masoned sable (black), the whole surmounted by an antique crown (the proper name for the "Irish" crown) or (gold).

Without bothering to rush to my resources, I'd bet someone already owns a red shield with a tower on it as their coat of arms. Now would a herald have kittens if he saw your tattoo? Probably not, as it would be obvious that there was no intent to usurp the heraldic property of another person in adopting what is, after all, personal body ornamentation. However, if the tower was on a ordinary shaped shield, he most definitely would arch an eyebrow in disapproval.

My advice to anyone contemplating an heraldic tattoo would be to stick to the buckle and strap devise of a clansman, and avoid using any "shield of arms".

Do I have a tattoo? No. Why? Because I have seen far too many second rate jobs. If the ink-slinger does a crappy job -- for what ever reason -- you are stuck with a bad tattoo pretty much for the rest of your life. To my mind that's Pascal's wager, and I don't think I'll take it up.