Kinda like an NSTokenField for iOS (see Messages / Mail apps).
See the "TokenFieldExample" app for details on usage. It's limited at the moment to one tokenising field and a content view below because it's pulled straight from one of my apps. Multiple field support requires tweaking.
This control is dual licensed: You can use it for free under the BSD licence below or, If you require non-attribution you can purchase the commercial licence available at http://www.cocoacontrols.com/authors/thermogl
Copyright (c) 2012 Tom Irving. All rights reserved.
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THIS SOFTWARE IS PROVIDED BY TOM IRVING "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL TOM IRVING OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.