Initially, the Sage said No…
The Dragon #335 Sage Advice column “Official Answers to Your Questions” includes this exchange:
Is it possible to have a weapon or an item enhanced with magic special abilities and imbued with psionic special abilities at the same time? If so, what would the creation process be like and how would you gauge market value?
Nothing in the Expanded Psionics Handbook suggests that such an item couldn’t exist. Assuming you were adding both kinds of special abilities at the same time, you’d just need to meet all the prerequisites (although spells or powers required could be contributed from other sources as normal).
For example, a +1 keen psychokinetic longsword would require the creator to have both the Craft Magic Arms and Armor feat and the Craft Psionic Arms and Armor feat, and he would have to supply the keen edge spell and the concussion blast power. It might well be easier to create one “part” of the item first (for instance, a +1 keen longsword), then bring in a second crafter to add the second “part” (the psychokinetic ability). (82)
(Emphasis mine. The Sage at this time is Andy Collins. The FAQ repeats this exchange almost verbatim (64).) By mandating that the weapon's creation requires both the feat Craft Magic Arms and Armor and the feat Craft Psionic Arms and Armor, the Sage, by extension, implies a craftsman can create a combination item using both Craft Universal Item and Craft Wondrous Item but could not create a purely psionic item using the feat Craft Wondrous Item (the first line of its benefit reading, "You can create any wondrous item whose prerequisites you meet") and could not create a purely magic item using the feat Craft Universal Item (the first line of its benefit reading, "You can create any universal psionic item whose prerequisites you meet").
Later, he changes his mind.
…Then he says Yes, sort of…
Two years later, writing in the Magic Item Compendium on Psionics and Crafting Magic Items, Andy Collins says
Many of the items in this book can also be created by a character with the appropriate psionic item creation feat.
For the purpose of meeting item prerequisites, a character who has the Craft Psionic Arms and Armor feat is treated as having Craft Magic Arms and Armor. Likewise, a character who has Craft Universal Item meets the feat prerequisite for items that require Craft Wondrous Item.
If an item includes a spell prerequisite, but the effect of the item does not directly implement that spell, then a psionic power of similar flavor can be substituted. If the item replicates a spell effect, then only the psionic version of that spell or a psionic power that replicates the same effect can be used to satisfy the prerequisite. (232)
So good for him for clarifying a little, I guess? Note that this lines up nicely with the rules for Magic–Psionic Transparency (XPH 55-6) and that this information is absent from FAQ. (Also, note that it's unstated whether this works in reverse, allowing a creature with the feat Craft Wondrous Item to make items with a prerequisite of Craft Universal Item, for example, but this DM would rule such is the case; no reason to give psions that peculiar and obscure advantage, and it's in keeping with transparency.)
Thus, while a creator must still manifest concussion blast and cast keen edge to make that +1 keen psychokinetic longsword, a creator needs only the feat Craft Psionic Arms and Armor, not, as previously mentioned, both that feat and the feat Craft Magic Arms and Armor. (Also, using the above rules only the most restrictive of DMs would prohibit a psion from manifesting psionic keen edge—instead of actually casting keen edge—to create that +1 keen psychokinetic longsword.)
…And of course there's a feat for doing it, too
A DM must determine if the Magic Item Compendium's rules extends to all equivalent items or only to magic and psionic arms and armor and wondrous and universal items. If it doesn't, there's this feat:
Chameleon Crafting (Dragon #349 89)
You can craft magic items that can duplicate psionic powers, or psionic items that duplicate magic powers.
Prerequisite: Any one item creation feat, ability to cast 1st-level spells, ability to manifest 1st-level powers.
Benefit: You can place any spell or a power that you know into any items you create. The item crafted determines if the effect is magical or psionic. For example, a psion/sorcerer with the Imprint Stone feat could create a psionic shocking grasp stone. Likewise, if the same character had the Brew Potion feat, she could create a magic potion of my light. The XP cost for an item created with this feat equals 1.5 times the item’s standard XP cost.
(Although a strict, take-no-prisoners, rules-as-written reading of this feat allows spells with a range of personal to be placed in a potion (as the example does with the power my light), this reader suggests that this feat perhaps inadvertently (and erroneously) expands the mandate of the feat Brew Potion. This is, however, beyond this answer's scope, and a question better left for the individual DM.)
Given the examples, the feat's likely intended to allow creating of specific type of magic items with psionic effects (like potions and wands with psionic powers) and vice versa (like djores and power stones with magic spells), but with such a feat and the DM's approval, a craftsman possessing only the feat Chameleon Crafting and, for example, the feat Craft Rod could create custom magic items having DM-determined psionic prerequisites but such items would have the listed increased XP cost.