When Apple (AAPL) announced in 2008 that it was pulling out of Macworld — no longer exhibiting its products or staging Steve Jobs’ closely-watched keynotes — many wondered whether the venerable expo could survive.

It was touch and go there for a while, but it turns out there is money to be made providing a venue where third-party vendors and Apple’s preternaturally loyal customers can get together once a year.

So this week in San Francisco’s Moscone West convention center, some 300 companies will be exhibiting their wares at the freshly renamed Macworld|iWorld — a new brand, explains general manager Paul Kent, that formalizes the show’s evolution since the rise of the iPhone and iPad.

Kent has taken a page from Austin’s South by Southwest, setting up performance spaces and galleries and booking a roster of Apple-flavored name-brand artists, including jam-band Moe, writer Susan Orlean, Public Enemy’s Hank Shocklee and the creators of South Park.

But at its heart, Macworld|iWorld is about the software and accessories on display — some silly, some substantive, some a little scary. Here are the themes that caught our eye on Day 1:

• Big Brother. Appmospheric is pushing its Teen Agree app for GPS-equipped smartphones that lets parents monitor where their kids are driving, how fast they are going and — on Android phones only — whether they are texting at the same time.

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  Bottle openers. We spotted three different iPhone cases with built-in church keys, one from Opena Case that slides from the bottom and two from Intoxicase that are affixed to the back. Intoxicase also makes a free app that counts how many brews you’ve opened.

• Brushes and pens. Nomad sells two models for the iPad that mix capacitive bristles with natural fibers. Kickstarter-funded Adonit makes three — Jot Classic, Jot Mini, Jot Pro — for fine lines. And Smile makes a pen for marking up PDFs.
• Camera attachments. iPro and Olloclip sell systems that let you add fish-eye, wide-angle and, in the case of Olloclip, macro lenses to the iPhone 4 and 4S. For videographers, iSupport makes stabilizers with handles and a socket where third-party lenses can be screwed in.

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  Microphones. To improve on the built-in model, Mic-W makes its iSeries “professional” mics that plug into the headphone jack. Blue Microphones has one with a pop filter and a shock mount that wouldn’t look out of place on David Letterman’s desk.

• Industrial-strength cases. RokForm makes a series of magnesium and aluminum iPhone cases — with locks and lanyards — that look like they’re ready to go to Afghanistan. Gid Development’s Bodydock system includes a kickstand and “Sweet Spot” magnets for attaching to fabrics.
• Waterproofing. Watershed makes drybags for the iPhone and iPad. DryCASE’s claims its cases are waterproof to 100 feet.

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  iPad holders. To make it easier to hold an iPad with one hand, Grablet offers an attachment with big plastic clips and an adjustable pad. Octa’s Tablet Tail comes in two pieces: a vacuum dock and a flexible WhaleTail that looks just like it sounds. We still haven’t seen the perfect iPad pillow for watching movies in bed.

• Hipstamatic for video. Global Delight has a cool new app called Game Your Video packed with easy-to-apply filters, special effects and themes that makes the chore of editing raw video into, well, a game. $1.99 on iTunes.