The first day of the Consensus 2016 Hackathon saw over 20 blockchain entrepreneurs pitch their ideas and concepts to a wide array of developers from all over the world.

Gathered from as far away as Asia, Australia, and Europe, both entrepreneurs and Hackathon participants weighed concepts ranging from an app that verifies its user doesn’t have a sexually transmitted disease to a bank built from scratch on the blockchain.

The tools provided to coders, technologists and other Hackathon participants were brought to the table by some of the biggest names in the bitcoin and blockchain space today.

Event organizer and president of Blockchain University Robert Schwentker said that he hopes the wide range of blockchain tools and cash prizes inspire a new wave of distributed ledger development.

Schwentker told CoinDesk:

An estimated 150 developers are attending the Building Blocks Hackathon, hosted at the Microsoft Technology Center in Times Square. The winner, set to be announced tomorrow, will receive $5,000 in cash as well as additional prizes. Other prizes for building on specific software are also being offered by event sponsors.

The pitches presented by the blockchain entrepreneurs present during today's sessions captured a wide range possible applications. Notable concepts included an app concept that allows farmers to pre-sell digital tokens in exchange for fresh food, a distributed autonomous organization (DAO) aimed at boosting transparency in labor unions,  a "cryptobank", and an app that lets potential romantic partners prove they don’t have any sexually transmitted diseases. That particular idea raised a notable round of applause from the audience.

Citing an Economist article from last year which reported lower rates of rape and sexually transmitted disease in certain areas following the legalization of prostitution, software developer Kevin Moran described how sex industry workers might be able to use such an app to automatically let partners know when they might be in danger.

Moran told attendees:

Bill Bodell, another entrepreneur present, pitched a project called FarmShare that functioned as a modernized version of an existing business model for what he called a "decentralized community supported agriculture platform".

Bodel later argued that the idea benefits more clearly as it scales.

"It seems like a pretty easy model to update with blockchain. Turn those shares into a token which then can be exchanged for fresh food," he told CoinDesk. "The key is to scale it from being a single farm to being a network or community of farms and other food entrepreneurs."

Hugo O'Connor of BitTrade Labs flew in from Australia to pitch his idea for UnionD, which seeks to help prevent corruption by decentralizing the organization structure of labor unions.

“My idea is to decentralize the union movement by putting unions on the blockchain as a decentralized autonomous organization," he said. "Think of it as Uber for unions.”

While many of the pitches involved non-financial applications of blockchain technology, software developer Benson Evans pitched his idea to build a bank that can manage cryptocurrencies and digital assets.

"Telling consumers about public addresses and private keys is not the way to go to get bitcoin and cryptocurrencies to scale," he said. "We need to somehow build systems above that, simplify the process, and see public addresses and private keys as lower level."

Before the entrepreneurs and coders started the speed-dating portion of the Hackathon, when they mingled among each other on the sixth floor of Microsoft's spacious New York offices, event sponsors offered demos on the product and code being made available to participants.

Schwentker estimates that half the coders in attendance have never worked with blockchain, adding that tools that streamline development are fundamental to the education process and help participants meet competition goals during the two-day event.

Representatives from Microsoft's Azure computing platform demonstrated how to access their “sandbox” environment for building blockchain applications. IBM showed how developers could build their products using a customized version of the Fabric distributed ledger being created by Hyperledger, a project of which it is a founding member.

Three projects under the ConsenSys umbrella — BlockApps, Truffle, and Ether.Camp — all demoed how participants might use their tools as well.

Among the sponsor challenges, which included cash and digital currency-denominated prizes, was an offer by Deloitte to fly the team it dubs most commercially viable to Atlanta, Georgia, to work directly with its innovation team.

"We want you to crate a killer app that will benefit our customers," Deloitte's director of payments integrity, Prakash Santhana, told attendees.

At last year's Consensus 2015 Makeathon, the killer app ended up being Tierion, a startup that hashes receipt data on a blockchain.  After it's founder Wayne Vaughan, earlier this week announced he raised $1m he offered a reward of a single bitcoin – worth about $450 at press time – to the hackathon attendee or CoinDesk reader who provides him the best definition of a "blockchain".

The two-day event precedes the Consensus 2016 blockchain technology event, which kicks off Monday at 7am. The sold-out, three-day event consists of 143 speakers, including Delaware Governor Jack Markell, 21 Inc. CEO Balaji Srinivasan, and R3CEV CEO David Rutter.

Photos by Michael del Castillo for CoinDesk