D&Dtools

You create a set of triggering conditions for the targeted scroll so that if these conditions are met, the spell on the scroll is cast upon you as if you were spending a standard action to cast the scroll yourself.
If the scroll contains a spell that is not on your spell list, it is not cast when the triggering condition occurs and the magic of the spell phylactery dissipates.
Any limitations involved in your reading the scroll normally (such as a minimum ability score or requiring a caster level check) still apply, and if they are not met, the spell phylactery magic dissipates.
The conditions needed to bring the spell into effect must be clear, although they can be general.
For example, a spell phylactery with a scroll of water breathing might prescribe that any time you are plunged into or otherwise engulfed in water or similar liquid, the water breathing scroll instantly comes into effect.
If complicated or convoluted conditions are prescribed, the spell phylactery may fail when called on.
The scroll is activated based solely on the stated conditions, regardless of whether you want it to.
The scroll prepared with this spell must be bound to your arm or forehead (usually rolled tightly or placed in a small box for this purpose) and counts as a bracer or headband in terms of space limitations for magic items.
The spell on the scroll must be of a spell level no higher than one-third your caster level (rounded down, maximum 5th level).
The spell on the scroll must be one that affects your person, and the triggering conditions must be clear as defined in the contingency spell.
If another person wears the spell phylactery, the magic of this spell ends.
You may remove and rewear the spell phylactery without penalty, but if 24 hours pass without your wearing it, the magic of the spell phylactery ends.
The termination of this spell does not harm the spell on the scroll.