While the iPhone and even the iPod touch are fairly expensive pieces of consumer electronics, the average age of users is falling fast as people upgrade and price of the entry level devices drops.

There's also a more subtle trend, which sees parents letting their kids use their iDevices: something that can end in near disaster and subsequent purchase of an iPod touch for those little hands to smear butter over.

One company that's picked up on such behaviour is One Circle Inc, which is specifically making games for parents and children to enjoy together.

We caught up with principal Antonia Chappell to discuss the size of the potential market as well as its first app. Also called One Circle, it enables players to build and share interactive characters.

Pocket Gamer: To begin with, can you explain what you mean by the secondary iPhone audience and why you think it's important?

Antonia Chappell: By secondary audience, I'm referring to the people (kids especially), who are playing with a primary user's hardware and driving sales of apps.

For example, I buy apps for my son, who is eight, while data from mobile ad company Greystripe reports that 59 percent of iPhone Moms let their kids use their phones. This doesn't include the dads and other people who are passing over their iPhones and touches.

If the statistics are accurate and 46 percent of iPhone users and 28 percent of iPod touch users have kids, given the current 50+ million installed base, this is a very influential group. And, these secondary users are not only influencing the things being purchased, but also the apps being developed.

What was the inspiration behind One Circle?

The name was primarily inspired by the ability to create things with the app using 'one circle'. When I was playing with early concepts, I began challenging myself to see what I could do using only basic shapes. Eventually, I paired it down to a circle and discovered there was a lot I could create.

I discussed this with my partner and we also liked the idea of a Responsive Interactive Character (RIC) world represented by a circle, which you see on the Play screen when you zoom out to the world view. This also influenced the name.

You need to keep the interactivity simple but why did you think five circles creates enough variation for kids/people to make characters?

Think about how many things you can create with LEGO bricks. We wanted to keep it simple, as you mention, but we also wanted this to be a creative activity that would spark people's imaginations. Kids are great at using simple objects to create incredible things, something I think us grown-ups could remember how to do more often.

People are making really inventive things with the app. I've seen pirate RICs with eye patches and swords, animals with ears and tails, and more. Since RIC behaviours are impacted by designs, the experience becomes even richer once you begin interacting.

Do you have any plans to extend the experience - maybe with the RICs interacting together or being part of a more gamic experience?

We want to add additional features and hope to take advantage of some OS 3.0 features in future versions.

I also think there is a lot more to expand on in the social media and sharing arena . We're hoping our customers give us feedback and help us identify the things that are important to them.

Do you think there are other ways you can encourage kids and parents to interact together on the iPhone such as more structured co-operative play or is free form better?

I think that both forms are valid, but haven't seen much structured co-operative play integrated in current apps. I do enjoy seeing parents showing their kids how to do things on the iPhone or, in many instances, watching the kids show their parents something.

One of our goals in the development of One Circle was to make the experience collaborative.

Kids (of all ages) love to show off their creations and people always want to poke and interact with the characters and are then inspired to build and share their own. The sharing feature also makes this a less solitary experience, and there are more ways we'd like to expand co-operative play in the future.

Do you have any plans to extend the One Circle experience from iPhone to other platforms i.e. Facebook?

We are looking at other platforms and our company is developing responsive interactive characters for mobile and marketing applications.

I personally love the ability to create animated AIM icons. My little AIM RIC is incredibly expressive, even though the animation is simple, and it really personalises my IMs.

Thanks to Antonia for her time.

You can see more about the One Circle concept via its website.