Hard to believe, but March is here, and with this lambing-lion of a month comes Engadget's first-ever Expand conference in San Francisco. It also marks the impending culmination of our first-ever Insert Coin: New Challengers competition. Late last year, we asked makers to submit their projects for a chance to win $25,000 in prizes. We whittled that list down to 10 semifinalists and asked you to help up get it down to a final five, which will go up in front of our all-star panel of judges on March 16th and 17th. Finalist voting closed yesterday, and we've tallied the 5 projects that will be demoed on stage. Check them out after the break, and be sure to follow our coverage at Expand for a chance to help pick the Grand Prize and People's Choice winners.

Make-a-Play

Announcing the Insert Coin New Challengers finalists!

We do get worried from time to time that plopping kids in front of TV sets and video games can have a detrimental effect on their imaginations -- that's why it's great to see a bit of technology that actually encourages kids to let their little brains run wild. This Arduino-based stage lets the little ones create their own programmed puppet show, complete with lights, music, movement and more.

Smart Knob

Here's a keypad for your front door, doing away with all those pesky keys. Smart Knob is targeted at property managers, renters and other folks who need to give a number of people access to a single entrance. The easy-to-install device is compatible with standard circular deadbolts, utilizing codes that are issued by property owners or by calling an automated phone system.

SmartPulse

An open-source fitness device, Smartpulse can tether to Android and iOS via Bluetooth 4.0. The device's designers are in the process of finalizing the API to let fellow developers get the most out of this thumb-sized smart oximeter.

Snapzoom

Are you getting the most out of your smartphone's camera? Probably not, if you don't have an adapter like Snapzoom. The device helps attach all manner of phones to all manner of scopes, including binoculars, telescopes, and zoom lenses, so you can look at the stars or do a little birdwatching.

Ziphius

Ziphius is a partially-submerged aquatic drone that can be controlled via iOS or Android devices. It has an on-board HD camera for first-person visuals, so users can rock some augmented reality as they cruise the open waters. Its makers also plan to open Ziphius' API, to let game and app developers get the most out of the little guy.