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There are already dozens of over-the-top messaging services in the mobile app stores and more are emerging each month, but one trait they all tend to share is a desire to replace SMS. Invi, however, has a different take on messaging. It wants to build a better, richer SMS client, but as for message delivery, it’s leaving that to the carriers.

Invi launched the first iteration of its app in Google Play(s goog) back in December, but on Tuesday it’s releasing its fully formed software, which integrates completely with the phone’s SMS capabilities. It also announced it has closed a $3 million seed round from Hutchison Whampoa Chairman Li Ka-Shing’s Horizon Ventures, actor Ashton Kutcher, Guy Oseary’s Grade-A Investments and several other Silicon Valley angels.

The new app is designed to step in for Android’s SMS and MMS client, replacing it with a visually appealing interface. It brings images and multimedia to the forefront, instead of just embedding them as thumbnails or files in the text stream. The previous version of the app – which was download a few hundred thousand times — only supported in-network messaging to other Invi users, but with full SMS support, users can text anyone with a mobile phone and anyone can contact an Invi user using their regular phone number. Think of it like Apple’s iMessage(s aapl) or BlackBerry Messenger(s bby), except prettier.

According to VP of Marketing Tali Saar, Invi’s SMS-focused model separates it from the other OTT messaging providers. WhatsApp and Viber built their huge global user bases by offering an extremely cheap alternative to SMS. That model has been very popular overseas where carriers typically still charge by the text message, but in the U.S. most customers have unlimited data plans (whether they like it or not), so here the cost of SMS isn’t an issue. Invi is going after those users who want a richer texting experience, but don’t want to give up on the core capabilities and reach of SMS, Saar said.

Invi has plans to expand to expand to both iOS and Windows Phone,(s MSFT) Saar said, though it won’t be able to offer its full feature set on the iPhone due to Apple’s tighter control over the messaging client. It also wants to introduce more features to the client. People are attaching all kinds of things to text messages, from videos to songs; Saar said Invi’s goal is to turn its app into a place where users can share any kind of content – and maybe earn some referral fees along the way.